Using thin-film transistor with thick oxygen-doped Si-Zn-Sn-O channel and patterned Pt/NiO capping layer to enhance ultraviolet light sensing performance

Abstract To improve the photodetection performance of thin-film transistor (TFT)-based ultraviolet photodetectors (UVPDs), using thick channel layers to promote photocurrent (I ph ) or using thin channel layers to suppress dark current (I dark ) is a typical trade-off. In this work, UVPDs based on oxygen-doped Si-Zn-Sn-O (SZTO) TFT with a stack of Pt/NiO capping layers (CLs) to release the trade-off between I dark and I ph are demonstrated. The Pt CL creates a wide depletion region in the channel layer to allow the use of thick channels, but still maintains low I dark , while the NiO CL forms a pn heterojunction to provide additional photogenerated carriers and enhance I ph under UV irradiation. Experimental results show that the proposed 95-nm-thick oxygen-doped SZTO TFT with a stack Pt/NiO dual CLs exhibits excellent photoresponsivity of 2026 A/W and photosensitivity of 9.3×10 7 A/A, which are about 76× and 82.5× higher than the conventional 45-nm-thick SZTO TFT under 275 nm UV irradiation.