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

In recent years \beta -Ga 2 O 3 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 -Ga 2 O 3 single crystals and highly crystalline \beta -Ga 2 O 3 thin films require high temperature, long processing times and, often, expensive tools that limit integration with other technologies. Amorphous Ga 2 O 3 has not been studied as intensely as \beta -Ga 2 O 3 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 Ga 2 O 3 thin films deposited at room temperature by magnetron sputtering. Control of the Ga 2 O 3 thin films resistivity over a wide range is demonstrated by controlling the deposition power and pressure. The TFTs show a threshold voltage ( \text{V}_{{\mathrm {T}}} ) of 0.92 V, saturation mobility ( \mu _{{\mathrm {sat}}} ) of 0.511 cm 2 / \text{V}\cdot \text{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}\text{A} /W ( \text{V}_{{\mathrm {G}}} =0 V) and 10 4 A/W ( \text{V}_{{\mathrm {G}}} =6 V), gain of 10 3 , specific detectivity of 10 15 Jones and a photosensitivity of 10 7 .