Al2O3/ $\beta $ -Ga2O3(-201) Interface Improvement Through Piranha Pretreatment and Postdeposition Annealing

In this letter, we report on the improvement of atomic layer deposited (ALD) Al2O3/$\beta $–Ga2O3(-201) interface quality through piranha pretreatment and postdeposition annealing (PDA). The high quality interface is verified via the temperature dependent capacitance–voltage ($C$–$V$) and photo-assisted (deep UV)$C$–$V$measurements, considering its ultra wide bandgap of 4.8 eV for$\beta $-Ga2O3. A low$C$–$V$hysteresis of 0.1 V from the measurement frequency of 1 kHz to 1 MHz is obtained, compared with the hysteresis of 0.45 V without piranha optimization. An average interface trap density$({\mathrm{ D}}_{\mathrm {it}})$of$2.3 \times 10^{11}$cm$^{\mathrm {-2}}\cdot $eV$^{\mathrm {-1}}$is extracted from the photo$C$–$V$measurements. Piranha pretreatments and PDA turn out to be an effective way to improve the ALD Al2O3/$\beta $–Ga2O3(-201) interface for future high quality Ga2O3metal–oxide–semiconductor field-effect transistors.