The above figure shows the approach developed by Cornell researchers to create a
"universal substrate" for semiconductors, eliminating many of the traditional obstacles to
semiconductor manufacturing. A "substrate" is the surface onto which materials
are deposited. In conventional methods (a), where the twisted top layer is
not present, deposited materials can often develop defects which make them unusable.
The Cornell technique (b) involves bonding a thin film at a misaligned angle on the substrate, so that defect-free
single crystals of many previously incompatible materials can be grown on it. This could lead to a new
generation of semiconductors for microelectronics and optical electronics.
(Figure courtesy of F.E. Ejeckam, M. L. Seaford, and Y.H. Lo at Cornell University and H. Q. Hou and B. E. Hammons at Sandia
Labs. Seaford is also affiliated with the Air Force Wright Patterson Lab. Text adapted from
Cornell University News Release on this topic.)
In the March 31, 1997 issue of Applied Physics Letters, Yu-Hwa Lo and his colleagues at Cornell announce that they have created
a thin gallium arsenide film whose crystal axis is rotated slightly relative to that of the gallium arsenide
substrate onto which it was deposited. Onto the gallium arsenide surface, the researchers successfully deposited crystals of
indium gallium phosphide, gallium antimonide, and indium antimonide. If gallium nitride (mismatch of 20%)
could be deposited onto this surface, the researchers believe that
high-quality blue and ultraviolet semiconductor lasers might
result. They expect that their approach could allow computer
chips of many different types to exist on the same motherboard.
(Left) This image, taken with a transmission electron microscope, shows an indium antimonide thin film on a
traditional gallium arsenide substrate. Note the defects at the boundaries, making this material
unsuitable as a semiconductor.
(Right) A thin intermediate layer of gallium arsenide is twist-bonded to the gallium arsenide
substrate in a technique developed by Cornell scientists. The boundaries are defect-free,
making it suitable as a semiconductor. The Cornell technique opens the door to a revolution in electronics
manufacturing.
Photos by F.E. Ejeckam, M. L. Seaford, and Y.H. Lo, Cornell University; and
H. Q. Hou and B. E. Hammons, Sandia Labs. Seaford is also affiliated with the Air Force
Wright Patterson Lab. Caption text adapted from
Cornell University News Release on this topic.
This research is described in the March 31,
1997 issue of Applied Physics Letters.
