RF Diamond Transistors: Current Status and Future Prospects

RF diamond transistors have been developed on a hydrogen-terminated surface conductive layer. f T and f max of 23 and 25 GHz, respectively, have been achieved in a diamond MISFET with a 0.2 µm gate length. Utilizing de-embedding and small-signal equivalent circuit analysis, parasitic components are extracted. The intrinsic f T and f max of the 0.2-µm-gate diamond MISFET are estimated to be 26 and 36 GHz, respectively. In this report, some of the challenging steps in device fabrication processes such as the development of a low-resistivity ohmic layer, a high-quality gate insulator and acceptor density control technology, toward high-power and high-frequency diamond transistors with high reliability, are introduced.