Russell Ohl - Session II

Hoddeson:

Yesterday we left off discussing reactions to the discovery of the junction; you had just finished telling me how Mervin Kelly understood the significance immediately. Now, I want to ask you a question about the junction discover. It is referred to in several articles as an accident. I wonder if you would agree with that.

Ohl:

No, I don’t think so. I think it was an outcome of the work. You see, we knew there was such a thing as two types of silicon and we had been calling them X-type and Y-type. Jack Scaff and I worked closely together and Jack said he would wager that that was due to an impurity in it, but we didn’t know what the impurity was. He said it was very similar to his experience with copper oxide. They finally tracked down the properties of copper oxide as being due to an impurity that was in it and he thought it should be something in the silicon. I had been working with the idea that we wanted very high purity silicon to get a good front-to-back ratio, a high value. So, that’s the way it stood. We recognized there were two types of silicon and we called one an X-type and the other a Y-type because we didn’t know too much about it. Then we got a melt through that showed the two types in one melt and a junction in between. Jack and I got together on that, in fact, I had proposed the N and P designation because of the polarities that developed due to the photo— voltaic effect, the point contact and the thermal effects. They all pointed to the same thing that when one material would become negative, the other would become positive. So, we named one N-type and the other P-type. Jack said, it sounded very good to him, so he said I’ll go ahead and use that designation. That’s the way it started. So these people that say this is purely an accident, I wouldn’t agree to it.

Hoddeson:

Lark-Horovitz also got involved. I found a letter in your file — this one. I don’t know if it relates or not.

Ohl:

Lark-Horovitz thought he could do the same thing with germanian but then when he applied for a patent he found he couldn’t get it patented, because change to a similar element does not constitute invention. And, he was quite disappointed with that. I talked to him in Princeton University at a colloquium there and he said when I introduced myself, “I am acquainted with your work on paper.” And then we got to talking about it.

Hoddeson:

Did you develop more of a relationship with him after that? Or was there only that one meeting?

Ohl:

No, he was a friend of Becker and Becker did all the dealings with Lark-Horovitz. We sent him reports and that sort of thing, and they all went through Becker, J. A. Becker.

Hoddeson:

I see. And so the letter I have here dated September 16, 1942, is —

Ohl:

— just a note of record.

Hoddeson:

O. K. By the way, were you interpreting the results in terms of Wilson’s model of semiconductors at that time?

Ohl:

No. You see, I have a German mind. I had to have my own explanation. In some respects, from the standpoint of a student, it might sound silly. But from the standpoint of an experimental approach to the subject, it’s very useful because I had my theory clearly in mind and I knew all the details of it, and so I could work with it right along. As a matter of fact, if I took somebody else’s theory and their thinking, I would have to think back and then interpret it and then I would have trouble. So I preferred to work by myself and develop my own theory. And there’s a memorandum on that subject. You can, at your leisure, study this and you can have these…

Hoddeson:

At this point, before we go on, I would like to record some things you have already told me off the tape about Kelly’s attitude towards semiconductors. You’ve already mentioned on the tape how at a certain point Kelly clearly became very interested in what was happening. Now, I had not been aware of his opposite position in the early years and I would like you to tell me about that.

Ohl:

Well, Kelly was a vacuum tube man and he preferred to think that the use of solid state was not justified, that it could be done with vacuum tubes. And he did not evidently, have the full realization of the properties of the vacuum tube as far as electronic speed is concerned, the speed of the current going through the tube. But I had been vey familiar with it because I had worked with it as early as 1923 and recognized it; this was a real thing to me. I guess he didn’t have, the time to think it out. But I think some of that is described in some of the patents, some of the theory of that and that’s another thing that you have to study. I hate to call your attention to that but there is so much reference work to do on this that I think you will be swamped with it.

Hoddeson:

I don’t think there is any way out.

Ohl:

He had this attitude but he wasn’t in the picture for quite awhile. Bill Wilson had the job you see and Kelly wasn’t in it. And Buckley was head of the Laboratories and Bill Wilson reported to Buckley and, as I said, there was some peculiarity, Buckley didn’t seem to understand anything that was new. It seemed that his education stopped when he got his doctor’s degree. But then fortunately he would bring Kelly with him and if it came to a technical question Kelly was much more knowledgeable. Basically Kelly had an honest mind; he had a real good scientific mind, but he was human and he felt that all these thing could be done with electronics. They actually spent a lot of money trying to develop special vacuum tubes to work in the ten centimeter range — that was the S-band range, you know. They spent something like $100,000 just to get sample tubes. Then it took that much money to convince them that the solid state approach was a much more practical way because there were very difficult circuitry problems in the use of vacuum tubes and in the solid state you didn’t have any filament voltage, you know, and you just had to have the single battery supply. So it made the circuitry much simpler. You had better results with solid state devices from the standpoint of noise. I didn’t mention anything about the noise before. You see, as you got vacuum tubes to work at higher and higher frequencies you faced a higher and higher basic noise and there was no way to avoid that. The noise can be calculated from the velocity of the charged particles that pass through the device and that was fixed. So naturally with semiconductors you had very little velocity and very short distances so we were bound to have less noise, a lower temperature noise. An electron device which goes to increased velocities has higher noise levels. So the signal noise level served as a criterion. You get a more favorable signal-to-noise ratio with a solid state device because of the lower velocity of electrons. That was the situation that Kelly didn’t seem to understand until the danger of war came along. That changed the picture. When the British came over here, they had no detectors for microwaves. They didn’t have the solid state developed, we had it developed. So they spent a whole lot of time in the laboratories at Holmdel to get the information on the solid state. And that’s when I introduced the idea of the heat treatment of silicon. The British visitors were with me at the time. I’d said that I didn’t have time to develop this. I had too much work, I just simply couldn’t get at the investigation of the heat treatment of the surface but I had gotten some remarkable effects in my experimental investigations. They said, “Don’t worry about that, we have lots of people available and we’ll put them to work.” And they did. They took over the heat treatment for a short time.

Hoddeson:

When was this?

Ohl:

That was about 1939. They were just getting ready to get into the war. And that was the time that Kelly started to take an interest in solid state diodes. He called a conference in which Heising was present, the Chemical Department people, Jack Scaff and myself. And he was very irritated because I didn’t come to the conference on time. But I had train connections to make and I couldn’t quite make it, so I was about ten minutes late or something like that. Well, he said, “You should have taken an earlier train.” He was that sort of a fellow, you see, he couldn’t overlook a little thing like that. He’d just land on you with two feet. But I wasn’t scared of him. I just simply explained what it was and that was it, that was a fact, and he could either take it or leave it. There wasn’t anything he could do about it. But anyway, I explained to the people that were gathered there how we had learned to process the silicon, how we had learned to make a back contact, how we had learned to solder it fast, and how we had learned to polish the surfaces and fabricate it in quantity so we could manufacture it. And that was the turning point. After that, Kelly took a very constructive interest in it over and above Friis and Bown. That’s really the way it was. This was about 1939.

Hoddeson:

The tremendous number of visits to your laboratory I gather began after the war. Is that correct?

Ohl:

No, before the war. We were not at war with Germany or the Axis powers. But actually we were put on a wartime basis long before war was declared. And heck, we in the laboratory were on company-confidential basis you see which was kind of sponsored by the government. But still the government had not declared war so they couldn’t declare it a secret affair, but the company did. So we worked as though there was war long before, a year or two before, war was actually declared that is.

Hoddeson:

Who were some of the visitors to the laboratory before the war?

Ohl:

I have a terrible memory for names. And I can’t tell you but I can tell you where to find it. George Southworth has an accurate record of the visitors from Europe, and a lot of those people visited my laboratory, and you can get the names from his notes. You can also get them from Gus Mon.

Hoddeson:

I see. O.K. I suppose then that throughout the war the junction was considered private information.

Ohl:

Yes it was. Yes, actually, had to take the melts that were produced and cut the junction out of them, cut the end type material out of it and send the remaining P-type material to the British to fabricate. We did not break the confidential basis of the company information and turn that over to the British.

Hoddeson:

But the actual application of the junctions was postponed until after the war. Is that correct?

Ohl:

It was put on ice. Now, Kelly took charge of that and he kept it that way. He evidently had plans to mind long before he established the solid state group of Shockley, Brattain, Bardeen and the others. I personally deduced that there was a conflict of company policy at this time, that it didn’t fit in the organization to have this work come from Holmdel because Holmdel was a field laboratory in which radio was involved and especially receiver development. The solid state work was kind of an appendage to radio, but since I was doing it as an individual doing research, that was all right until Kelly got into power and he thought everything should be organized. And he may have gotten that training from Buckley because Buckley figured the company should be run like an army. But I objected to that because I had an understanding with Perrine when I came to work with the company that I would do radio work. With a patent record that was known to General Carty. I was allowed to go ahead doing exploratory work. Then approved by W. Wilson and so forth, I felt that it wasn’t up to Kelly to change all that history. And I stuck with it and, actually, I won out because they did not succeed in stopping that work at Holmdel.

Hoddeson:

During World War II you worked on the problem of making good a silicon diode for radar, along with others, both in and outside of Bell Laboratories. I wonder if you could comment on this a bit. DO you think that developments would have come out differently had the war not intervened?

Ohl:

Yes. It probably would have killed it. The forces that were at work were anxious to kill that semiconductor work and they wanted it to come out of Murray Hill if there was anything in it. I think they would have stopped it. They made something like four attempts to stop the work before the war.

Hoddeson:

You are suggesting that in a way the war was fortunate for the advancement of this research?

Ohl:

I was supported by the full power of the Patent Department to be allowed to continue this work.

Hoddeson:

Could you comment further on the problem of making silicon for radar during the war, and on how that problem contributed to what went on after the war?

Ohl:

Oh yes. You see, there was ever a constant moving towards shorter wavelengths for secrecy reasons. In military tactics you want to develop a new method of doing something and for awhile you have an advantage because the enemy does not know how to treat it. Finally, through spy information and other sources of knowledgeability, they would learn how to counter the new method. So, we first started in S-band. And then there was a lot of pressure to get to new wavelengths. And that was the time we went to X-band. You know what the bands are? In order to go to X-band we had to have some source of beating oscillator — we had no tubes — and we had had oscillator tubes in S-band but they were not very good, so what happened was the first, they used crystal detectors that generated the second harmonic from L-band oscillators and generated S-band beating oscillator. And then we went from S-band — when we got oscillator tubes on the S-band — we went from S-band to the X-band by means of harmonic producers. We used the third harmonic there and that give us enough beating oscillator current on X-band to make receivers. And then they used those receivers to develop the tubes to generate the X-band directly from vacuum tubes. At first, they wanted to make the shielded type detector for use at X-band, but when we got it in shape and started to get it in manufacture they found some manufacturing difficulties that they couldn’t overcome. But there was 50 much pressure on using the X-band that we, in desperation, modified the contacting wire that we used in S-band for X-band diodes. Fortunately, we could do it by simply changing the size of the wire in the S-band design and shortening the spring. Then they worked beautifully at X-band. So then we stopped development of the shielded type detector and started all over again to build a new one for the K-band. We had time to get into that and we went through the same thing. We used X-band oscillators to generate harmonics in the K-band region, the third harmonic, you see. We finally got enough power to power a first detector in the K-band region and that opened up the K—band. Then at MIT laboratories they developed a tube oscillator, a completely different type of oscillator you see, the signal-to-noise ratio didn’t play such a dominating part because the energy levels are much higher and you could get away with the use of electronics at these higher energy levels. But electronics couldn’t be used at the lower receiver levels because of the adverse signal-to-noise ratio. So then the K-band was developed and they actually made radars and got them in shape for use but that was near the end of the war. Then when the war had ended, there was a great pressure to get K over 2 in shape to use in waveguide transmission tests. They decided to try to use the waveguide for telephone purposes and then would develop the K over 2. Again, in order to get a K over 2 we had to use the crystal harmonic producers and we used the K-band oscillators to drive those. We used the harmonic to get into the 6 millimeter region. So you see, the development of these crystals was vital to the development — the opening up — of the millimeter wave region. That was what we started to do in l933 and ‘34; that was the objective of the work. We knew that it would work eventually because I had proven with the spark transmitters that these crystals would respond to 4.3 millimeter waves. So we weren’t working in the blind. We knew they would work but we still had to standardize it and this work that I did was to get it processed so that it could be manufactured by the Western Electric Company and all the research work was done in my laboratory at Holmdel.

Hoddeson:

During the war, you worked very closely both with the Rad Lab at MIT, which you mentioned, and with Whippany.

Ohl:

They didn’t do so much. No, no.

Hoddeson:

Was the major cooperation then with MIT?

Ohl:

Yes. MIT was the major one.

Hoddeson:

And didn’t Pennsylvania get involved also?

Ohl:

University of Pennsylvania? Well, they did to some degree, but it never amounted to much. They didn’t get into any of the secret specification, development and manufacture.

Hoddeson:

What about the interactions with the British?

Ohl:

Oh well, now that was direct, but it gradually shifted to MIT and the British would come to us through MIT. The Radiation Laboratory was sponsored by the Government. The Government took control of this situation. And the British would come over and work through the Radiation Laboratory and then come down to Holmdel. And the K-band shielded detector was sponsored by a fellow by the name of Bleany with whom I later on became quite friendly. I convinced him that the shielded type detector was the way to go and .he recommended it to MIT and they finally adopted it and coded it.

Hoddeson:

Was Hans Bethe involved at all? Brattain mentioned him in this connection.

Ohl:

Yes, he made a few contributions but did mostly theoretical work. He indicated at times that cold discharge was involved in the theory after he had read my memorandum.

Hoddeson:

Did he come to the Labs at all, or was this done by mail?

Ohl:

No. Be worked it out on paper.

Hoddeson:

He didn’t actually visit?

Ohl:

No. Now, there’s an angle he that should be talked about. The company, at certain times, was very tight. They would spend a million dollars on something that would be sponsored by the administration, but they wouldn’t spend the money that was sponsored by the people who knew something about the subject. Now, I wanted to get very high purity silicon, hyper-purity silicon, and Jack and I had agreed that if we got the hyper-purity silicon we could control the doping. You see, in the silicon work we recognized that there were two types of carriers. There’s an N-type and a P-type. And if we wanted to have a semiconductor in which the p-type was dominant, then we had to dope it for P-type and we didn’t want to have stray doping in there that would tend to cause it to be N-type. Because as soon as you got a semiconductor doped with both P-type and N-type you had a conductor. It wouldn’t rectify. When you get the right balance you don’t have a rectifier; there’s nothing you can do about it.

Hoddeson:

Were these discussions carried out before or after the war?

Ohl:

During the war, early part of the war. Now, we wanted to get high purity silicon and then we contacted DuPont and they wanted a quarter of a million dollars to make something like 25 pounds of it.

Hoddeson:

Was that a lot of money?

Ohl:

Well, it was a lot of money then. Our company wouldn’t spend it. And that was the trouble with Friis and Bown. When it came to that sort of thing their nerves just disappeared. They didn’t have the courage to go out on a limb and approve such an expenditure. And they wouldn’t put up a fight and I couldn’t do it by myself. But if Southworth were with me, he would have sponsored it. So, we informed the MIT people about the situation and they said, all right, we will do it. So the Government spent a quarter of a million dollars directly as a part-time effort and got the DuPont people to manufacture and set up the machinery and processes and they got hyper-purity silicon. And the MIT people then would agree to give us a part of it, like if they furnished a hundred pounds to MIT, maybe they’d give us five or ten pounds. But that was enough for our experimental work because silicon went a long way. It’s a light material you see; it has a fairly low density and you could make quite a few melts and the melt would give you a lot of samples. So we got it that way.

Hoddeson:

Brattain mentions that the NDRC contract during the war was• set up by Harvey Fletcher and Professor Tait. Do you recall anything about this?

Ohl:

I had nothing to do with that.

Hoddeson:

I see. Now after the war you and Jansky and Southworth were moved into another building on the Holmdel property.

Ohl:

Now let’s stay during the war. Yes. During the war, the contracts were a pain in the neck to me because I would be taken off research work on the basis that we were desperately in need of something that could only be manufactured in my laboratory and would I please manufacture these things to get the job going? I would have to. I realized I had to cooperate because you can’t fight City Hall all the time. So I should stop my research endeavors for a period and go into semiconductor manufacturing just to get the job going. In wartime these things have to be done. Research was working very close to the wartime effort because that was the only way they could get the stuff done on a secret basis. We worked hand and mouth in order to keep ahead of of the techniques that were developed by the enemy countries. So the pressure was pretty great to do both the research and have the research incorporated in the plant. But Jack Scat f was the intermediary and he would take over the work as fast as he could and develop it in their department and relieve me of that type of approach. Nevertheless, it was there and this oscillated back and forth all through the War. The heat treatment especially was something we developed. And you will find some of the early memoranda on heat treatment that was signed by Treuting, Storks and myself and you have to read that to get the heart of it.

Hoddeson:

The visits from Compton and Bush were during the war.

Ohl:

Yes.

Hoddeson:

Do you recall anything about those visits? We had this discussion in part off the tape yesterday.

Ohl:

Yes. That was shortly after the junction had been discovered.

Hoddeson:

How did they happen to come and visit?

Ohl:

Well, Kelly informed them. You see that was known to the Government but it was strictly secret. It wasn’t a top secret, it was next to the top secret rating.

Hoddeson:

Did they come together, or separately?

Ohl:

Well, Compton came to my laboratory. The others just came in to see the laboratory and then left in other fields: They specialized in different things.

Hoddeson:

I see. Do you recall some details about the visit from Compton?

Ohl:

Yes. He visited the laboratory and he asked all kinds of questions and I demonstrated the np junction, I told him all about the early history and how it had been developed, and what silicon was for and that it would work in the millimeter range and all that sort of thing. I gave him all the information that I had recorded, that described She development of the whole subject and finally culminated in the np junction, and that we named it and why we named it and how Jack Scaff and I worked on it, and he understood all this. We could work pretty fast you see. He was a technical man who was well versed in this sort of thing. So after he and I had spent quite a few hours there talking in detail, he left and made that remark that he thought it was a fine piece of work. And he was directly responsible to President Roosevelt.

Hoddeson:

Now, why were you and Jansky and Southworth moved to another building on the Holmdel property after the war?

Ohl:

Well, I don’t know why but I think that was decided by Sown and Friis. And maybe Kelly was in on it. I don’t know.

Hoddeson:

It was about a half a mile away, wasn’t it?

Ohl:

Yes. I wouldn’t know. I was never consulted. They simply told us the result.

Hoddeson:

Were you happy with this? Was it a better place to work?

Ohl:

No. No. Kelly came over and I had been established in the laboratory and he looked at my laboratory and I told him, I said, “This stuff that we’re building here for ionic implantation requires very heavy equipment.” I said “It bothered me because it was an old building and the strength of it was not very certain. And just below me was a good friend of mine.” I said, “It cost me a good deal of uneasiness.” And shortly after that they cleared out the whole basement of the building and moved me down to the basement and gave me the whole basement. And that was on the ground floor. It wasn’t a real basement because it was a half-depth basement; there were windows in it that looked right out on the properties. But it was a basement, and they fixed it up, insulated it and got it into good shape. I was pretty well located there and then they build a new annex to the main building and this surprised me very much because, for some reason or another, it was decided that I should have one of the wings of that. And I got an enormously large laboratory, with private offices and large storage places and everything and all the facilities that I needed. And this was when I was going into my 50’s. I was getting to be 50 years old and I was slowing down. It was late. But in that laboratory I developed the implantation work.

Hoddeson:

I’d like to ask you a question about the work immediately after the war. There seems to have been at least three lines that you were following, maybe four. One was the development of microwave equipment to be used in repeaters for transcontinental broadcast radio. Another was the developments that ran parallel to the transistor work carried out by the Murray Bill solid state group. And a third was the ion implantation work.

Ohl:

That was mine.

Hoddeson:

Yes. Now all of this work was going on at the same time, wasn’t it?

Ohl:

Oh yes.

Hoddeson:

And was the diffusing phosphorus part of the ion implantation?

Ohl:

The way that was started was like this.

Hoddeson:

Which one now?

Ohl:

The np, it was a puzzle. We determined we had two types of silicon, n and p-type. But we didn’t know what the impurities were. And Jack Scaff felt — we smelled acyteline — it was a carbide. I didn’t know what it was. I didn’t have my mind made up but Henry Theuerer thought it was phosphorus. So he made a test. Actually, I don’t know whether he did it or I did. He took p-type silicon and the surface was polished. We polished the surface and he heated that in a furnace in the presence of phosphorus vapor and he got a surface that showed photovoltaic properties. And that’s as far as he took it because we were busy with something else. But he told me about it and I remembered it. And after the war was over and I started work on my own. I went back to research again. I decided to repeat Henry Theuerer’s experiment and see if I could get the same result. I tried with red phosphorus and I did not get the same result. Then I went to yellow phosphorus and I got the same. Then I used red phosphorus and put water vapor in and I got the result. Then I decided that it was very difficult to diffuse phosphorus into the silicon lattice because of the size of the phosphorus molecule. But you had to have the ionized phosphorus molecule. Now maybe you don’t have a chemical background but that is the situation. When you ionize phosphorus you reduce its size quite a bit and then you could get it into the crystal lattice by theta mal diffusion. So I figured that if I could ionize the phosphorus, I wouldn’t have to go to indirect methods but I could actually diffuse it directly into the surface. And that was the start of ionic bombardment and that is described in one of these memorandums. And I went to different substances. And incidentally, when I built this apparatus at this time, Karl Jansky came in and that was the last time I saw him.

Hoddeson:

Wasn’t Pearson also working on ionic bombardment?

Ohl:

Who?

Hoddeson:

Gerald Pearson.

Ohl:

NO. Well, some of the other people made a few little tests and wrote a report. I didn’t work that way. I carried it through to a finish you see, I made a definite research project out of it and there was nobody to say “Stop it here.” I just continued right on with it.

Hoddeson:

Were you interacting closely in this period with the three new groups that were formed in 1945: The Solid State group under Morgan and Shockley; the Physical Electronics group under Wooldridge; and Fisk’s group on Electron Dynamics?

Ohl:

I interacted with the solid state group, but not much with the other two.

Hoddeson:

Then let’s focus on the detailed nature of your interactions with the solid state group.

Ohl:

Well, the solid state work: it was a one way street. They got my information but I didn’t get the information from them.

Hoddeson:

Were you aware of the experiments that Brattain and Bardeen were then doing?

Ohl:

Only indirectly through Brattain and Shockley. Bardeen was not an experimentalist. Shockley wasn’t an experimentalist. Brattain was an experimentalist. And then they had other people. They had another fellow, several people, that were electrical men, that worked with the physicists. You see, Shockley, Bardeen and Brattain were not electrical men, and they would get electrical information on how to build the apparatus and what kind of circuits. They would frequently get that from me. And I’d show them. In fact, I showed them how to build D. C. amplifiers. And they would come down to my laboratory and find out how to do this sort of thing. But I didn’t get any advantage in my work from them. Now the point of that’s involved as my work was patented, you see. And I was a dangerous man to deal with because they would say something that would give me a little information and I could convert it immediately into patentable material. So that was bad for Murray Hill. This is politics again. I didn’t get into politics until after the war, then I began to feel the weight of Murray Hill politics and I detested that. I was kept out of it because I think they thought it was dangerous to give me that information. This is my personal contention. I deduced this from the way things were.

Hoddeson:

Shall we advance now to the contact potential work of 1947?

Ohl:

I thought that contact potential work was very interesting and in fact I think somebody ought to take that up and continue research on that. It never came to a complete investigation. Brattain really started that and I took up the work in a different direction after Brattain had started it. It was originally started by. Kelvin, Lord Kelvin.

Hoddeson:

And then Brattain picked it up in the ‘30’s?

Ohl:

No, when he worked on the transistor he picked it up.

Hoddeson:

So he picked it up in the mid ‘40’s.

Ohl:

In the late ‘40’s, and the early ‘50’s. You see, what Brattain did was he made an apparatus to measure the surface potential in a vacuum and put different gases in it and he investigated that. He finally dropped it. He wrote a memorandum and he dropped it. And then later on I took it up. I didn’t want to work in the vacuum, but I wanted to find out what was happening on the surface and I put my samples in the high vacuum and took them out quickly and then found the decay curve, the change in curvature. And this was something that Brattain had not found. And I could formulate the thing and then by continuing the curve, I could find out what the potential was in the vacuum and what it could finally decay to. Because I could formulate the thing and Brattain had not done that. And that is when we found out the effect of moisture on the silicon surface. This is where my early training in electrochemistry comes into play. Electro-chemistry is said by some to be a branch of physical chemistry, and I became interested in the surface. When you think of the surface chemistry, you think of absorption and you think of chemabsorption and you know what the difference is. So I became interested in using, this Kelvin method that Brattain had been using to give me some knowledge of the surface conditions and it did and that is when I found out the effect that you get in a vacuum when you took it out and put it under atmospheric pressure. It developed in a logarithmic form; it was very definite; you could easily formulate it. You could project the curve to zero time and find out what the value was in the vacuum and you could do this very accurately and then you could take that formula by mathematical manipulation you could tell when it became asymptotic and wouldn’t give you any appreciable change any longer. So this is a measurement of the difference in the photoelectric effect between two substances. And by using platinum as a standard, you could have a great stability on a lot of them, a good reference. At one time I used gold for a reference and that worked out pretty well; I used high purity gold for a reference. That was a second choice. Platinum was the first choice. I obtained very high purity platinum made up by the Baker Company in Newark to make these electrodes. It was quite expensive, but I used it for my reference electrodes. Some electrons escape from the surface into free space. This generates an electric dipole. Therefore, you have an electric field. If you have an electrode above it, and you have another electrode material just like the top electrode moving as an arm going through the gap in between there is a variation in potential on the top electrode. This represents the dipole potential of the sample. Then all you have to do is measure the voltage of the sample to ground. To do this, a battery potential, is applied until the field is neutralized. Then you’ve got a direct measurement of the difference in contact potential. Now this has to be done with very high impedance circuits. I used input impedances of the order of 10 million megohms. And I used special electronic vacuum tubes that were made by the Raytheon Company that had input resistance of about $10 sup 13$ ohms. This did the job. But now we could build that same apparatus and use transistors and it would be greatly simplified. We could use the metal oxide semiconductor transistor that has a very high input resistance. I was often sorry that I wasn’t in a position to carry on the work now that the new transistors are available. Stopping that job was not the right thing to do. It was just partly done; we just scratched the surface. In the University, if you were doing graduate work, that would be a fine project to get into. It would take pretty high skills to do it through.

Hoddeson:

I understand that Shockley was trying to add a third element to your diode, I think before the war.

Ohl:

I did that. I was trying to.

Hoddeson:

Was Shockley involved in that too?

Ohl:

Shockley saw my demonstrations and I actually built some and had then in a vacuum, and started to make some measurements.

Hoddeson:

But I thought that never worked.

Ohl:

Well, it showed some indications. But here is the philosophy behind that.

Hoddeson:

Was this just before the war?

Ohl:

No, this was after the war. Maybe it was during the war. During the war I had periods when I could do research work on the evaporating of metal on the polished surfaces. The Western Electric Company on occasion sent representatives down to my laboratories to find out how to do it. This went on all the time. I had a personal policy that I did not withhold information for my own personal benefit. I felt that I was working for a company, and I felt that the company was entitled to my results. I felt that if I found anything useful they could have it because if I could find that, then I could find something else. That is what kept my work going. I worked on that policy.

Hoddeson:

Now about this third element?

Ohl:

So I built things with the third element. And I got effects from the third element.

Hoddeson:

What was the third element?

Ohl:

The third element was a plating of rhodium in between an oxidized surface and a plating of silicon was plated on top of that third element. This was a very very thin plating of metal to be a conductor in between the two silicon surfaces. The idea was to control the current that would got through the silicon. And thus hopefully we could get the equivalent of a vacuum tube. But that was faulty because the difficulty was that we still had the high capacity to contend with and we could not develop sufficiently low input impedance because of the capacity. We were just following the wrong course. But I did try to make something of that sort of arrangement.

Hoddeson:

Becker had been working on that earlier.

Ohl:

I didn’t know about this.

Hoddeson:

I remember Raymond Sears told me they were watching him do it. And they said “Joe, you need to understand what is going on.” He didn’t understand the phenomenon, but he was trying.

Ohl:

I understood what was going on. What we didn’t realize before the transistor was invented, what I personally didn’t realize, was that you could have a very low impedance input into a circuit and have a high impedance output and get a gain. But Jansky had been working on input circuits that were low impedance input and high impedance output. But they were for impedance transformation and they did not give you much gain. But there was a fellow Gibney, who worked with the solid state group who realized the advantages that could be derived from having a low impedance input and a high impedance output either. Brattain or Shockley seemed to realize that. But I always felt that the transistor was really partly an invention of Gibney who was an electrical engineer.

Hoddeson:

Is he someone I should talk to, if I can?

Ohl:

He was never given any credit for his work.

Hoddeson:

Is he someone who is worth making a visit to?

Ohl:

I don’t know. It might be.

Hoddeson:

There is very little information available about Gibney’s specific contribution.

Ohl:

I know. He made a valuable suggestion that was simply taken up by the solid state group namely, the three men that worked on that and gobbled everything up and called it theirs.

Hoddeson:

Did you know Gibney?

Ohl:

I met him, but I didn’t have close contact with him. But Walter Brattain, he was too darned honest, let the cat out of the bag and told me about it. We were good friends you know. You see a lot of the information was interchanged informally. For instance, Henry Theuerer would tell me about things that he had found out by the grapevine about what people in other companies were doing and he would pass the information along and once we got a towhold on it and knew what was happening, we would grab it and put it into use right away. Really research is made up •by people who have a certain amount of larceny in their nature. Another man who came into this who liked to make a big fuss about what he was doing was a fellow that left the company and then worked with Texas Instruments.

Hoddeson:

Gordon Teal.

Ohl:

I knew Gordon Teal. He made some stuff for me. But I don’t think he was entitled to his claims because he would take on other peoples’ work and try to develop it rapidly. He struck me as being not too astute in research work. But he was very astute in grabbing a hold of something and jumping on the cart as though it was going some pl1ace and getting what he could out of it. He was a nice fellow though.

Hoddeson:

I gathered that impression myself just in looking at his articles.

Ohl:

I want to tell you something about that. You see, Gordon Teal made a big thing out of the fact that he developed growing single crystals. But much earlier than that Bob Treuting and I had decided that we should try to grow single crystals of silicon. This is in the early part of the war. Long before, maybe five years before, the transistor work, Bob Treuting said well he would talk to his people to see if they would allow him to do this. He said he thought he could grow them. And Bob had a Ph.D. from Yale in Metallurgy and was very well equipped. But he died when he was quite young. He was a very capable metallurgist and was willing to do that type of research and he was anxious to do it. But when he talked to Earl Schumacher about it he would get the cuff. Now in the metallurgy department they had the same bottle neck as I had in my department. Jack Scaff and some of his men would be willing to work along and do this and that. They would come up to Earl Schumacher and they would hit a stumbling block. So one day Friis and Bown decided that I should be transferred to the metallurgical group. Kelly talked about it to Schumacher. And Kelly was convinced and he said, “If Ohl does not want to be transferred, don’t push him.” And that was the end of it. I knew I couldn’t work under those conditions; So you see Kelly was on my side after that.

Hoddeson:

DO you believe that Shockley’s decision in 1945 or 46 to focus on silicon and germanium derived directly from his earlier conversations with you in Holmdel?

Ohl:

I think it had a great idea to do with it. The discovery of the NP junction was a new discovery and they hadn’t known about that. That, as I pointed out, was the breakthrough in solid state physics that they were looking for and hadn’t found. Nobody had found that and that was really a great breakthrough. That was a landmark in solid state physics. And of course they say that was accidental, but the discovery of the transistor effect was just as accidental. Brattain wasn’t looking for it. Very often all great discoveries come that way. They are not a matter of great genius, but they happen because the person who finds them is trained in that sort of work and he recognizes it. They are made that way.

Hoddeson:

Before we move on up to the silicon solar battery, I want to ask you if you think it’s worth spending a couple of minutes discussing the development of the microwave equipment to be used in repeators for the transcontinental broadcast. Do you think we should talk about that?

Ohl:

Yes. The curves that I showed you were made at the time we were developing the microwave equipment for the transcontinental microwave radio. That was part of the work that was done to help out in the problems that appeared in incorporating transistors in that microwave equipment. At the time I was supposed to develop a harmonic producer that would handle power up to 50 watts. And Friis assured me that they had a very powerful oscillator that would give me 50 watts of fundamental power. Therefore, if I could design something that could handle power levels of 50 watts, that could be very useful. But it turned out that Friis was misinformed and such power levels were not attainable. So we had to drop it down to a lower power level. Then I developed what was placed, in the shape of a horseshoe or a semi-circle, underneath a contact and the contact was gotten by pushing the silicon up against it. We could make very low impedance diodes that way. These diodes were able to handle quite large powers. That was developed in conjunction with the transcontinental radio microwave. Then later on we found that with the power available we could just take a heavy tungston wire and put that down on the surface and make a sufficiently rugged silicon device that could handle the power that was available, so we used that.

Hoddeson:

Did the silicon solar battery work come out of the work on ionic bombardment?

Ohl:

No. You see, there were two ways you could go. A chemist could use diffusion and make the NP junction layer by means of diffusion. Fuller and Chapin and someone else developed that line of attack. I couldn’t follow that line of attack. But I reasoned that I could do the same thing and do it in a more desirable way if I could use implantation into the surface. By regulating the temperature of the silicon into which the implantation was taking place, and controlling the velocity with which the ions struck the surface, I could determine how deep I could go Therefore having control of the depth, we could, have control of whether we want photovoltaic response, or whether we want harmonic producing devices or whether we want to make diodes that would be good in the fractional millimeter range.

Hoddeson:

How did you happen on this?

Ohl:

I was working on trying to make photo-active surfaces and trying to treat silicon surfaces so that you have a very very thin layer of change in impurity content. See before that in order to make diodes out of material that had impurities in it, we treated the surface by oxidizing it in water vapor at an elevated temperature, about 1000 degrees C. And when we did that, we depended on the difference of the rate of diffusion of the impurity in the silicon into the oxidized layer that was formed on the surface. And we found that we had left over a very thin layer of high purity material. And this layer was very thin, so that when we made a contact to it we could get a space charge effect. And then having the space charge effect, if we passed current through in one direction there would be no space charge effect and the current would go through easily but if we passed current in the other direction, there would be a very great space charge effect. So we could get a very high resistance in the back direction. This gave us a substantial front to back ratio. Then when I was moved over to the Roberts house, I started work to see if we couldn’t get control of these surfaces so that we could get surfaces that were very thin. These would be used to generate harmonics particularly and show a detection effect in the submillimeter range. That’s how that work was started, the implantation. This was a direct attack on the subject. This wasn’t gratuitous. I actually went after it with the intention of developing a method that was different from the diffusion method because I felt that with the diffusion method you couldn’t control it; there was no uniform barrier. You have a gradual change form a high purity on a surface to the impurity on the inside and that’s not what I wanted. I wanted a very thin controllable layer that I could use at the very high frequencies. It was on alternate method. I could do it because I had the electronics background for making these experiments. Now the chemist, the straight chemist could not do this. He did not have the proper training. But all through this work you will notice that the attacks that were made in my laboratory were made in a way that an electrochemist would have done it, by one who was trained in electrical engineering as well as in inorganic chemistry.

Hoddeson:

How does your work differ from the work that was done later by Fuller and Chapin?

Ohl:

Somewhat different.

Hoddeson:

Could you inform me about these differences?

Ohl:

They produced the photo-cells by following through the earlier work that Theuerer had done, diffusing it in a gaseous medium in a furnace. The diffused boron into an n-type material in order to get the layer, the PN-junction. This is not the method that Theuerer had used. He used P-type and diffused phosphorus into the surfaces. In diffusing the boron into the layer, there were some pretty severe chemical problems. And then they did another thing. They made a very low resistance contact on the back of the cells. The result was that they and a photocell that had very low internal resistance, so when they put it in sunlight and they converted the sunlight into electricity they could work from a low resistance cell into a high resistance load and get close to a 100% efficiency. Whereas in my cells I had a high impedance and I could only work from a higher impedance into an equivalent impedance and I got about half the efficiency that they had. So they improved the efficiency. I knew that you could get these high efficiencies and I could calculate it. Kingsbury and I had worked out the theory of this effect in making the curves in our paper. We had done all the mathematics that was not published.

Hoddeson:

Why not?

Ohl:

Well, that was a matter of creating a paper that was readable and could be recorded thing, but would not be tedious in reading and Kingsbury was very astute in making these complicated calculations. It involved optical calculations that were a study by themselves and it was decided that we didn’t want to put it in the paper even as an appendix, because the methods were well-known to a few people who worked in the art, but we felt they wouldn’t add anything to the paper. Maybe it was not a proper decision. The paper should have been published in the American Physical Society Journal and the appendix should have been added. It should not have been published in the Bell System Technical Journal, because it was too important a paper. But at the time we were just anxious to get the paper out. The pressure was pretty high and you know the trouble you have when you try to get a paper through the Bell System.

Hoddeson:

Do you recall your reaction to the work of Parson, Fuller and Chapin when it was published?

Ohl:

Was Pearson in on that?

Hoddeson:

Yes.

Ohl:

I know it was Fuller and Chapin, but I didn’t remember who the third person was.

Hoddeson:

Yes, Pearson.

Ohl:

Well, that was the thing. I had correspondence with the AT&T Company on that and the chief engineer of the AT&T Company finally wrote to me and explained to me that when the question came up of the patentability, they thought there was enough novelty in their manufacturing process to take out a patent on it. They tied all their publicity on the solar battery to that patent; it was an improvement patent on my basic patent.

Hoddeson:

Were they aware of this themselves?

Ohl:

Oh yes.

Hoddeson:

Did they talk to you about it?

Ohl:

No, they didn’t talk about it. This was a high echelon decision in the Company. We didn’t have anything to do with it.

Hoddeson:

Who were in this high echelon?

Ohl:

Well, the chief engineer of the AT&T Company, the president of Bell Laboratories, the head of the publicity department, the head of the patent department and so forth.

Hoddeson:

I don’t understand why it was better for them to do it that way.

Ohl:

This was just company policy, this is something in which the men who worked on it had no say so at all. We weren’t even informed about it. When the publicity was released, Jim Fisk, who is a very forth-right and honest man, got up before the publicity people and there were some very well-known scientific reporters in the audience. He got up and told about my early work on this and how it developed into the transistor and solar cell and all that sort of thing. But then when the publicity came out, they chopped out all of my work. I never found out why, but they chopped all that out. It was censored; it was like somebody had taken a knife or hatchet and simply decapitated the early work. And when he wrote that book he wanted to get into that and give more credit to that early work and that was cut out and he was only allowed to put that one reference in.

Hoddeson:

This is, then, you suggest, a result of the Bell Company’s editing?

Ohl:

All of this was supposed to come from Murray Hill, and none of it came from Murray Hill! This is what you are going to be up against, but you can write the history as I told you because that is right. That is the way it was. If it comes to the Bell Laboratories you may or may not be cut off. But perhaps with the new regime, Baker and the new persons at the AT&T Company and so forth may see it in a different light. And you may not be up against that.

Hoddeson:

You still don’t have any idea as to why it happened?

Ohl:

I don’t know.

Hoddeson:

Would Fisk know?

Ohl:

He might know. But this might be a touchy subject and you might not be able to get it out of him. Baker might know but he was just getting into executive work at that time and I doubt whether he was in on it.

Hoddeson:

Would Fuller know?

Ohl:

I doubt whether he knew.

Hoddeson:

Did you know Fuller?

Ohl:

I have met him, but I didn’t know him too well. But the Chief Engineer of the AT&T Company would know something about it. But I didn’t want to carry on that correspondence, because I realized you would just simply be up against an inversible decision. It was like talking to the mayor of a big city after he had made a decision. You just couldn’t get anywhere. I have on record my protest about that. I wrote to Mr. Kappel about the situation and that was put on record, quite a long protest. I have a copy someplace with pictures. I photographed the first solar battery and all that sort of thing.

Hoddeson:

That would be useful to me. It’s getting late and we will have to stop soon. I would like to get this on tape: there are obviously many gaps in the story we are piecing together. I’m sure you’ll see them when you go over the transcript. Could you make a note about those gaps which you feel we need to fill in later on? You could add these notes to the transcript and/or dictate them into a tape recorder. We might go on if I can find the necessary funding to arrange another interview, or perhaps an extended telephone interview.

Ohl:

It might be possible for you to come out here some other time.

Hoddeson:

I hope so. We left out something earlier which is a gap and perhaps this is a good time to go back to it. You mentioned a double detection system which you build in Colorado…

Ohl:

Oh yes. In Colorado I wanted to build a double detection receiver, because it was a critical time and that work was coming through. Now Friis made a big point — he claims to have built the first double detection receiver that was .ever built. But I don’t think that is true. I think the first double detection receiver that was ever built was built in France. The effect of double detection was generally known. At that time I thought I would like to experiment with one, so I built it, not with the idea that it was novel to me, because I already knew about it, I built this just because I was interested. And when I was through with it I found that for some reason or other it didn’t compare with the sensitivity of an amateur type of receiver. I had an amateur receiver that used some miniature tubes that I had, developed in the Westinghouse Company. They were unique because they had silver plates and. silver parts in them. That was put in there because the studies of silver in the literature indicated that silver would occlude only oxygen and that could be eliminated by heating silver. Then you would have a vacuum tube that would hold its vacuum, which they did. The only thing used in quantities in those tubes, was phosphor getter. We didn’t expect to have thorium emission, but they developed thorium emission. So we had tubes that worked on half of the designed filament voltage and they would respond without having any plate battery. So all we had to do was have a volt and half voltage on the filament to excite them. There was enough electronic energy from there to the plates, so that we could receive east coast stations in Colorado. It turned out that by using the variometer receiver and having these very low capacity tubes in them, we could get the high sensitivity. But unfortunately, when you got this sensitivity you got a very high Q which cut off the voice side bands and they could not be used for voice reception. So for voice reception I used a double detection receiver. It used to amuse the other instructors on the faculty and they would come in there at night and they would listen to the programs from the Denver station; there were very few stations. Than another time I was interested in making microphones.

Hoddeson:

Was this also in Colorado?

Ohl:

Yes this was in Colorado. So I deduced that if you had a condenser and made it a part of an oscillator circuit; and if you varied the condenser capacity, you could get frequency modulation. So I got some doily hoops and spread some tin foil across them you see and put them close together. Then I connected them to an oscillator and spoke into them. And one of the other instructors, Julian Blair, took the receiver out in the hall. I told him how to tune it. Be tuned it so it received on the side of the resonance circuit and he was able to hear my voice over that kind of a circuit. It was interesting, because it was a novel application and it worked.

Hoddeson:

You mentioned to me earlier that there are two other recordings in existence somewhere, interview tapes that you made. I wonder if perhaps I could get copies of these to supplement this material we’ve been discussing. Undoubtedly some of it has been repeated here but I imagine there are things that weren’t repeated. The question is where are those tapes?

Ohl:

There is one in the library that record tapes at the University of Colorado. You write to the Physics Department and they have it.

Hoddeson:

I must ask them for a tape made by Russell Ohl? When?

Ohl:

About 1970.

Hoddeson:

What was it, an interview?

Ohl:

Yes.

Hoddeson:

How did it come to be placed in the Physics Department?

Ohl:

Because they recorded tapes of that sort. When anyone came to the department who had a background of what was going on in the department they made a tape and recorded it as a part of the history Of the school.

Hoddeson:

What was covered on that tape?

Ohl:

All about my experience and what I had there.

Hoddeson:

At Colorado?

Ohl:

Yes. About Dr. Oliver Lester and what we did.

Hoddeson:

I imagine there are things on that tape we haven’t covered here?

Ohl:

Yes.

Hoddeson:

I will try to get a copy. What about the other tape?

Ohl:

The other tape, was a talk to Frank Pilinghorn and he will give you the information. He is in the “Directory of Retired Members, October, 1975.” He knows where the tape is; he made the tape and he lives at 3426 Pahia Blance, West Laguna Hills. His telephone number is here too.

Hoddeson:

What is on the tape?

Ohl:

Well pretty much the same sort of story. I don’t remember what exactly is on it. We talked about two hours and he would ask questions and then we would talk back and forth.

Hoddeson:

What was the basic theme of his questions?

Ohl:

The story of what happened. You see, he was in the Laboratories too.

Hoddeson:

So then I suppose, he focused on work done at the Laboratories?

Ohl:

Yes

Hoddeson:

In which period?

Ohl:

Somewhat throughout the whole Laboratories, but I think more in the period in which he worked with me. He was at West Street, but he used to come down to Holmdel because he was in charge of making the equipment for the transatlantic short wave.

Hoddeson:

In what connection did he make this tape? Was it part of a history he was writing?

Ohl:

Yes, some history. He will tell you, there are so many organizations. I just can’t tell you off hand I think it had something to do with the IEEE. I think it would be easy enough to get in touch with him. You can call him on the telephone.

Hoddeson:

Sure. Well now before we break for lunch I would like to ask what the circumstances were that led you to leave Bell Laboratories?

Ohl:

Well I had come to a point…

Hoddeson:

When was this?

Ohl:

In 1958. I was 61 years old. When you get to a point in years you get tired. My wife said I didn’t look well. She said she thought it was about time that I retired. And then Russ and his family were about to go to Germany on a military assignment and we decided to go out there and be with the family for awhile before he left. See, Marilyn’s folks lived in this same place. So we decided to retire. I gave the company 30 days notice. That’s all. It was some hectic days I had, three and sometimes four young Ph.D.’s on my neck all day long wringing information out of me.

Hoddeson:

And then you came here?

Ohl:

No, then we went to Cambria. I rented a house there about 100 yards from the ocean, maybe not that far, nothing in between. And then I bought property and built a place and we moved in. It was just about a year after we had first come to Cambria. We lived there and thought we had a retirement place and I built a laboratory in that.

Hoddeson:

And what did you work on?

Ohl:

What didn’t I work on? I worked on water analysis, on gold analysis, gold ores and with a spectroscope. We collected rocks. And I cut rocks and polished them and made them into jewelry; my wife did the jewelry work and I did the laboratory work. And I had electroplating facilities, plated various things, and I did electronics work. I put in picture tubes for my neighbor friends. I built the electronics equipment in the new church that was built of which we were members. And I worked with the pastor and saw to it that he got all the electronic facilities, like his microphone with an FM transmitter, that he could walk around and talk into the loud speakers.

Hoddeson:

Did you maintain connection with the Bell Laboratories during that period?

Ohl:

No, not much. I retired early and I didn’t have social security so I had to earn some money and I did consulting work at first for the Hughes Aircraft Company. And then I made a contract with the Raytheon Company for one day a month. I did consulting work for the Texas Instruments Company and for an international patent firm in New York. Those are the main things and then I addressed the IRE, the Lions Club. But at no time was I permanently employed by any organization because I didn’t want to be, I retired because I was pretty well shot. It was a good thing. It took me two or three years to get back my health. I wired the house that we built. It was said that there was more copper in that than there was concrete.

Hoddeson:

We are supposed to be at lunch now. I think this is a good time to break. I want to thank you very, very much for this interview.

Ohl:

Oh, it was nothing. It was a pleasure.

Hoddeson:

I am sure there will be lots of additions to it.

Ohl:

I hope so.