Effect of 5 MeV proton irradiation damage on performance of beta-Ga2O3 photodetectors

Abstract

Planar thin film beta-Ga2O3 photodetectors were irradiated with 5 MeV protons at doses from 10(13) to 10(15) cm(-2), and the resulting effects on photocurrent, responsivity, quantum efficiency, and photo-to-dark current ratio at 254 nm wavelength were measured at both 25 and 150 degrees C. The photocurrent increased with dose due to the introduction of damage from nonionizing energy loss by the protons. The total calculated vacancy concentration increased from 5 x 10(15) to 5 x 10(17) cm(-3) over the dose range investigated. The dark current increased in proportion with the implant dose, leading to a decrease in the ratio of photocurrent to dark current. The photocurrent induced by 254 nm illumination increased with dose, from similar to 0.3 x 10(-7) A at 25 degrees C for a dose of 10(13) cm(-2) to similar to 10(-6) A at a dose of 10(15) cm(-2) at a fixed light intensity of 760 mu W/cm(2). The phototo- dark current ratio decreased from similar to 60 in the control samples to similar to 9 after proton doses of 10(15) cm(-2), with corresponding external quantum efficiencies of similar to 10(3) % in control samples, similar to 2 x 10(3) % for a dose of 10(13) cm(-2), and 10 4 % for a dose of 10(15) cm(-2). The mechanism for the increase in photocurrent is the introduction of gap states, since the dark current of the photodetectors was increased by illuminating with sub-bandgap (red or green laser light) for the proton irradiated samples. (C) 2016 American Vacuum Society.