Passive charged-particle radiation detection using pn junction in a diamond semiconductor

Radiation detection requires the use of materials rated for survivability in harsh environments. One such material, diamond, has been used for many years as a semiconductor for UV or radiation detection, but has suffered from the availability and nonideal crystallinity of natural sources. Recent advances in chemical vapor deposition has enabled the growth of diamond semiconductors with more tailored attributes for ideal and novel detector formats.

New research from Shimaoka et al. capitalizes on the recently developed pn junction in diamond semiconductors for the detection of charged radiation particles, which includes alpha, beta, and heavy ion particles. The pn junction has a stronger built-in electric field, which accelerates the generated charge carried toward the electrodes faster, than conventional diamond electronics which are based on Schottky barrier and metal-insulator-metal device structures. This increases the sensitivity of the device with lower applied bias.

The authors were able to use the diamond pn junction to detect incident alpha particles without applying an external bias to the device. The collection efficiency of the particles was 40 percent with an energy resolution of 30 percent. While the detector efficiency is similar to comparable devices, operation at zero bias voltage — i.e., without an external power source — is a clear advantage. In addition, the thin drift layer in the pn junction means that the gamma radiation has little effect on the alpha particle detection.

While the authors’ work focused on applications in alpha particle detection, future work will also be geared toward radiation measurements at the Fukushima power plant, and other important applications of diamond pn junctions such as the development of power electronic devices.

Source: “Diamond photovoltaic radiation sensor using pn junction,” by Takehiro Shimaoka, Satoshi Koizumi, and Manobu M. Tanaka, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5034413 .