High-performance p-channel diamond MOSFETs with alumina gate insulator

We evaluated diamond metal oxide semiconductor field effect transistors (MOSFETs) on (001) homoepitaxial and (110) preferentially oriented large-grain diamond films with an Al₂O₃ gate insulator and demonstrated their improved DC and RF characteristics (I_DS = -790 mA/mm and f_T = 45 GHz, which are the highest values for diamond FETs). Channel mobility evaluation and load-pull measurement were carried out for the first time for diamond MOSFETs. Even on a large-grain diamond substrate, a high channel mobility of 120 cm²/Vs was obtained. This is comparable to that of a SiC inversion layer. A power density of 2.14 W/mm was obtained at 1 GHz. This power density exceeded those of Si LDMOSFETs and GaAs FETs.