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

In recent years \beta -GaO 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 (8 mV/cm). However, \beta -GaO single crystals and highly crystalline \beta -GaO thin films require high temperature, long processing times and, often, expensive tools that limit integration with other technologies. Amorphous GaO has not been studied as intensely as \beta -GaO 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 GaO thin films deposited at room temperature by magnetron sputtering. Control of the GaO thin films resistivity over a wide range is demonstrated by controlling the deposition power and pressure. The TFTs show a threshold voltage ( \{V}_{\mathrm {T}} ) of 0.92 V, saturation mobility ( \mu _{\mathrm {sat}} ) of 0.511 cm/ \{V}\cdot \{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 and responsivity of 10^{2}\{A} /W ( \{V}_{\mathrm {G}} =0 V) and 104 A/W ( \{V}_{\mathrm {G}} =6 V), gain of 10, specific detectivity of 10 Jones and a photosensitivity of 10.