3.8 W/mm power density for ALD Al2 O 3 -based two-dimensional hole gas diamond MOSFET operating at saturation velocity

This paper reports the small-signal and large-signal performances at high drain voltage (V DS) ranging up to 60 V for a 0.5 μ m gate length two-dimensional hole gas (2DHG) diamond metal-oxide-semiconductor field-effect transistor (MOSFET) with a 100-nm-thick atomic-layer-deposited (ALD) Al2 O3 film on a IIa-type polycrystalline diamond substrate with a (110) preferential surface. This diamond FET demonstrated a cutoff frequency (f T) of 31 GHz, indicating that its carrier velocity was reaching 1.0 ×10 7 cm/s for the first time in diamond. In addition, a f T of 24 GHz was obtained at V DS = −60V, thus giving a f T × V DS product of 1.44 THz V. This diamond FET is promising for use as a high-frequency transistor under high voltage conditions. Under application of a high voltage, a maximum output power density of 3.8 W/mm (the highest in diamond) with an associated gain and power added efficiency were 11.6 dB and 23.1% was obtained when biased at V DS = −50V using a load-pull system at 1GHz.