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.