Low defect density and small I - V curve hysteresis in NiO/beta-Ga2O3 pn diode with a high PFOM of 0.65 GW/cm(2)

In this Letter, we report a high-performance NiO/beta-Ga2O3 pn heterojunction diode with an optimized interface by annealing. The electrical characteristics of the pn diode without annealing (PND) and with annealing (APND) are studied systematically. The APND device has a lower specific on-resistance of 4.1 m Omega cm(2), compared to that of the PND, 5.4 m Omega cm(2). Moreover, for the APND, a high breakdown voltage of 1630V with lower leakage current is achieved, which is 730V higher than that of the PND. The enhanced electrical performance of the APND leads to a record high power figure of merit of 0.65GW/cm(2) in Ga2O3-based pn diodes, which is among the best reported results in Ga2O3 power devices. In addition, the interface trap density of the diode decreases from 1.04x10(12) to 1.33x10(11)eV(-1) cm(-2) after annealing, contributing to much lower hysteresis. Simultaneously, the ideality factor n for the APND is steady at elevated temperatures due to the stable interface. The results of C - V characteristics reveal the bulk defects inside the nickel oxide film grown by sputtering, which are calculated by high- and low-frequency capacitance methods. X-ray photoelectron spectroscopy of NiO illustrates the reasons for the changes in the concentration of holes and defects in the film before and after annealing. This work paves the way for further improving the performance of Ga2O3 diode via interface engineering.