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

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).

Automated summary

In this study, a simple and cost-effective method for fabricating thin film transistors (TFTs) based on undoped amorphous Ga2O3 thin films deposited at room temperature by magnetron sputtering is discussed. The control of Ga2O3 thin film resistivity over a wide range is demonstrated by controlling the deposition power and pressure. These TFTs exhibit promising characteristics and have been evaluated as phototransistors under DUV radiation, showing high rejection ratio, responsivity, gain, detectivity, and photosensitivity.