High frequency single crystalline diamond MOSFET with high temperature (300 °C) ALD grown Al2O3 dielectric

In this paper, hydrogen terminated metal oxide semiconductor field effect transistors (MOSFETs) having a sub-micron gate length were fabricated on a single crystalline diamond sample using the 300 °C ALD grown Al2O3 as gate dielectric and passivation layer. The device shows a maximum output current density of 942 mA/mm and a lowest on-resistance of 6.2 Ω·mm at a VGS of −3 V. A maximum transconductance of 284 mS/mm was achieved. In addition, a high cut-off frequency of 41.3 GHz and a maximum oscillation frequency of 80.6 GHz were achieved. These are the highest values among the reported H-diamond MOSFETs with high temperature (>200 °C) grown dielectrics. The hole mobility is estimated to be 138 cm2/Vs at VGS = -3 V. The high carrier mobility contributes to the achievement of the high output current density. These results demonstrate that the high temperature grown Al2O3 dielectric has also a great potential to be used in high frequency H-diamond MOSFETs.