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

Planar thin film β-Ga2O3 photodetectors were irradiated with 5 MeV protons at doses from 1013 to 1015 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 °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 × 1015 to 5 × 1017 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 ∼0.3 × 10−7 A at 25 °C for a dose of 1013 cm−2 to ∼10−6 A at a dose of 1015 cm−2 at a fixed light intensity of 760 μW/cm2. The photo-to-dark current ratio decreased from ∼60 in the control samples to ∼9 after proton doses of 1015 cm−2, with corresponding external quantum efficiencies of ∼103% in control samples, ∼2 × 103% for a dose of 1013 cm−2, and 104% for a dose of 1015 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.