Investigating the effect of self-trapped holes in the current gain mechanism of β−Ga2O3 Schottky diode photodetectors

Abstract

Monoclinic gallium oxide (β−Ga2O3) has found great research interest in solar blind photodetector (SBP) applications due to its’ bandgap ∼4.85 eV and availability of high quality native crystal growth. Applications includ- ing missile guidance, flame detection, underwater/intersatellite communication and water purification systems require SBPs. β−Ga2O3 SBPs with high responsivity values have been published indicating internal gain in these devices. The gain has been attributed to accumulation of self-trapped hole (STH) below Schottky metal which the lowers Schot- tky barrier in these devices based on some approximations rather than a proper device simulation. In this paper, technology computer-aided design (TCAD) simulation of β−Ga2O3 SBPs are performed to numerically investigate the effect of low hole mobility STHs on Schottky barrier lowering (SBL). The simulations revealed that based on the theoretical hole mobility of 1 × 10−6 cm2V−1s−1 , photoconductive gain in β−Ga2O3 based photodetectors cannot be attributed to STH related hole accumulation near Schottky contact. It is found that hole mobility in the range of 1 × 10−10 cm2 V−1 s−1 − 1 × 10−12 cm2 V−1 s−1 is required to induce ∼ 0.3 eV of SBL potential. Unless such low hole mobility is reported either experimentally or theoretically, it is not reasonable to attribute gain to STH formation in these devices.