High-Current Metal Oxide Semiconductor Field-Effect Transistors on H-Terminated Diamond Surfaces and Their High-Frequency Operation

Metal semiconductor field-effect transistors (MESFETs) or metal oxide semiconductor FETs (MOSFETs) can be fabricated on hydrogen-terminated diamond without losing the surface hydrogen–carbon bonds and the surface adsorbates responsible for the surface carrier generation. Those FETs show their best performance in diamond transistors. The maximum drain current density is above 1 A/mm and the highest transconductance is 400 mS/mm. These values are comparable to those of modern FETs made of Si or III–V semiconductors. Regarding RF performance, the highest cutoff frequency reaches nearly 50 GHz. The power handling capability exceeds those of Si and GaAs at 1 GHz. The function of surface adsorbates and their stabilization are crucial for the application of diamond FETs.