High-sensitive solar-blind β-Ga2O3 thin film photodetector deposited by PLD optimizing growth temperature

Abstract

Metal-semiconductor-metal photodetectors are fabricated on β-Ga₂O₃ films grown by pulsed laser deposition at a wide range of temperatures from 400 to 650 °C. The films are β-phase with an oxygen deficiency and a bandgap of 4.65–4.84 eV. The photodetectors exhibit a narrow-band photocurrent with the main response peaked at 250 nm, which fits the solar-blind region. The epilayer deposited at 550 °C has the best crystal quality with a 4.84-eV bandgap, a responsivity of 8.5 A/W, a low dark current of 0.05 nA, an EQE of 4252 %, a detectivity of 9.5 × 10¹¹ Jones, and a slow kinetics of 0.2 s at room temperature. The photodetectors also possess a sublinear dependence of photoresponse upon illumination intensity, so the sensitivity lowers to 1 A/W at 26 μW/mm². The responsivity increases with heating up to 24 A/W at 250 °C. There is also a minor defect component with the onset at 340 nm (3.66 eV), associated with the defect levels at 0.62, 0.85, 1.02 and 1.18 eV below the conduction band. The growth temperature optimization allows us to suppress this defect-related band. Moreover, a shallow defect level with an activation energy of 0.2 eV is involved in the photoresponse mechanism.