Ultraviolet photodetectors based on Si-Zn-SnO thin film transistors with a stacked channel structure and a patterned NiO capping layer

Ultraviolet photodetectors (UVPDs) based on Si-Zn-SnO (SZTO) thin-film transistors (TFTs) with a stacked dual-channel layer (DCL) structure with different carrier concentration and NiO capping layer (CL) to alleviate the trade-off between dark current (I (dark)) and photocurrent (I (ph)) are reported. Experimental results show that under 275 nm irradiation, the proposed SZTO TFT UVPD with a 30 nm thick upper layer stacked on a 50 nm thick channel layer and a patterned NiO CL exhibit excellent photoresponsivity and photosensitivity up to 1672 A W-1 and 1.03 x 10(7) A A(-1), which is about 272 and 137 times higher than conventional 30 nm thick single-channel layer SZTO TFT. These improvements are due to the use of a DCL which forms a high-low junction to reduce the effective channel thickness and increasing the space for UV illumination and the use of NiO CL lowers the I (dark) and causes a considerable negative threshold voltage shift under UV irradiation to significantly boost the I (ph).