β-Ga2O3-based metal–oxide–semiconductor photodiodes with HfO2 as oxide

Abstract

We proposed β-Ga2O3-based metal–oxide–semiconductor (MOS) photodiodes using HfO2 as the oxide. Because of the larger band gap of HfO2 than that of β-Ga2O3 and the type-II band alignment at the HfO2/β-Ga2O3 interface, the MOS photodiodes exhibited almost no reduction in photoresponsivity against 254 nm light near zero external bias compared with Schottky photodiodes. In contrast, reverse leakage currents of the MOS photodiodes were substantially decreased compared with Schottky photodiodes owing to the increase in the apparent barrier height between the metal and the semiconductor. These features of the MOS photodiodes are beneficial for the future development of β-Ga2O3-based avalanche photodiodes without p–n junctions.