Elevated temperature performance of Si-implanted solar-blind β-Ga₂O₃ photodetectors

The temperature dependent photoresponse of planar photodetectors fabricated on β-Ga₂O₃ films grown on Al₂O₃ by metalorganic chemical vapor deposition to 254 nm wavelength, and blindness to 365 nm light, are reported over the range of 25-350 °C. Ohmic contacts were formed by Si-implantation and annealing at 900 °C, followed by deposition of Ti/Au metallization. The photocurrent induced by 254 nm illumination increased monotonically with temperature, from ∼2.5 × 10^-7 A at 25 °C to ∼2.2 × 10^-6 A at 350 °C at a fixed 254 nm light intensity of 760 μW/cm². The photosensitivity decreases at high temperatures in many photoconductors (thermal quenching), in sharp contrast to the photosensitivity increase with high temperatures in this study. This is ascribed to the presence of states in the gap of Ga₂O₃, whose presence was proven by exposure to below band-gap energy. In this case, the current still increased due to the presence of defect levels in the band gap and the generation of photocurrent is due to a transition between the valence or conduction band and impurity or defect levels within the band gap. The temperature dependent photo-to-dark current ratio for this wavelength was 328 at room temperature and decreased to ∼9 at 350 °C. The responsivity increased from 5 to 36 A/W over this temperature range, with corresponding external quantum efficiencies of 2.5 × 10³ % at 25 °C and 1.75 × 10⁴ % at 350 °C. Similarly large numbers reported for Ga₂O₃ photodetectors have previously been ascribed to carrier multiplication effects.