Tuning Electrical Properties of Amorphous Ga2O3 Thin Films for Deep UV Phototransistors

Abstract

In recent years beta-Ga2O3 thin films and crystals have gained attention as excellent candidates for transparent and high-power applications due to its wide band gap (4.6 - 4.9 eV) and large breakdown field (similar to 8 mV/cm). However, beta-Ga2O3 single crystals and highly crystalline beta-Ga2O3 thin films require high temperature, long processing times and, often, expensive tools that limit integration with other technologies. Amorphous Ga2O3 has not been studied as intensely as beta-Ga2O3 and mostly metal-semiconductor-metal (MSM) structures and diodes using this material have been reported. In this paper, we discuss a simple and economical method to fabricate thin film transistors (TFTs) based on un-doped amorphous Ga2O3 thin films deposited at room temperature by magnetron sputtering. Control of the Ga2O3 thin films resistivity over a wide range is demonstrated by controlling the deposition power and pressure. The TFTs show a threshold voltage (V-T) of 0.92 V, saturation mobility (mu(sat)) of 0.511 cm(2)/V.s and subthreshold slope (SS) of 83.62 mV/dec. More importantly, these devices have been evaluated as phototransistors, which has not been intensely studied yet. The phototransistors tested under DUV radiation exhibited a rejection ratio UV-Visible of 10(3) and responsivity of 10(2)A/W (V-G = 0 V) and 10(4) A/W (V-G = 6 V), gain of 10(3), specific detectivity of 10(15) Jones and a photosensitivity of 10(7).