Fully deep-UV transparent thin film transistors based on SrSnO₃

Ultra-wide band gap semiconductors are gaining attention for their promising properties for UV optoelectronics and UV transparent electronics. Among them, La-doped SrSnO₃ exhibits excellent properties both for deep-UV transparent oxide semiconductor (DUV TOS) and deep-UV transparent conducting oxide (DUV TCO). Here, we report the demonstration of thin film transistors (TFTs) with full deep-UV transparency based on SrSnO₃. The sequentially strain-relaxed La-doped SrSnO₃ films are grown on MgO (100) substrates with BaHfO₃ and SrHfO₃ buffer layer by pulsed laser deposition. TFT with a metal-insulator-semiconductor structure is fabricated using La-doped SrSnO₃ as the channel layer and LaScO₃ as the gate oxide. A highly La-doped SrSnO₃ is used as the gate, the source, and the drain electrodes to obtain good contact and deep-UV transparency. The resultant device shows a field effect mobility value of ~8 cm²·V^-1s^-1 and the I_ON/I_OFF ratio higher than 10⁷. The optical transmittance of the entire device (including the substrate) is found to be higher than 75% at 300 nm in wavelength.