Enhancement-mode normally-off β-Ga2O3:Si metal-semiconductor field-effect deep-ultraviolet phototransistor

In this work, a solar-blind ultraviolet (UV) photodetector based on a three-terminal enhancement-mode (E-mode) Si-doped β-Ga2O3 (β-Ga2O3:Si) metal-semiconductor field-effect transistor (MESFET) structure is demonstrated, whose threshold voltage (Vth) and subthreshold swing (SS) are 4.04 V and 1.4 V/dec, respectively. A 400-nm-thick β-Ga2O3:Si thin film is prepared on sapphire substrate by using metal-organic chemical vapor deposition (MOCVD) method. Controlling the channel currents by the Schottky gate voltage in the dark and under illuminations, the photodetector shows dark current (Idark) as low as 13.4 pA, photo-to-dark current ratio (PDCR) of 4.85×104 and linear dynamic range (LDR) of 29.6 dB, illuminated by 254 nm UV light of 245 μW cm-2. As the UV light is turned on and off, the output current rise and decay time (τr and τd) are 420 ms and 350 ms. Moreover, at drain voltage (Vds) of 5 V and gate voltage (Vgs) of 0 V, the responsivity (R), specific detectivity (D*) and external quantum efficiency (EQE) are achieved as 74 A W-1, 2.15×1014 cm Hz1/2 W-1 (Jones) and 3.6×104%, respectively.