Oxygen annealing impact on β -Ga2O3 MOSFETs: Improved pinch-off characteristic and output power density

In this Letter, we present direct current (DC), small signal radio frequency (RF), and large signals with pulsed and continuous wave (CW) studies and characterization on oxygen annealed (OA) β-Ga2O3 metal-oxide-semiconductor field-effect transistors (MOSFETs) with significantly improved CW output power density (Pout) when compared to other β-Ga2O3 RF devices. The OA process is found to be useful in compensating and neutralizing the donors in the unintentionally doped (UID) buffer layer and, hence, suppressing a second depletion effect in this UID layer. The device demonstrates a peak DC drain current of 200 mA/mm, a transconductance of 11 mS/mm, and an on/off ratio of 109. Small-signal RF characterization indicates a cut-off frequency and maximum oscillation frequency (fT/fmax) of 1.8 GHz and 4.2 GHz, respectively. The device also shows an output power (Pout)/peak power added efficiency (PAE)/gain of 0.4 W/mm/10%/3.2 dB and 0.43 W/mm/12%/3.6 dB for CW and pulsed signals, respectively, at an operation frequency of 1 GHz.