High performance broad-band ultraviolet-B to visible photodetection based on planar Al-Zn2SnO4-Al structure

Abstract

This work presents broad-band ultraviolet-B (UVB) to visible photodetection with a high responsivity and detectivity values based on a simple metal-Zn2SnO4 (ZTO) thin film-metal structure. Al-ZTO-Al based metal-semiconductor-metal planar structure shows high responsivity values of 9.25 A/W, 3.64 A/W, 0.71 A/W, and 0.44 A/W under 280 nm, 300 nm, 460 nm, and 550 nm illuminations at + 5 V bias with detectivity values of 4.06 × 1012 Jones, 1.6 × 1012 Jones, 3.1 × 1011 Jones, and 1.93 × 1011 Jones, respectively. The sensitivity values of ∼103, 4.7 × 102, 3.2 × 102, and 2.25 × 102 have been achieved under 280 nm, 300 nm, 460 nm, and 550 nm illuminations with external quantum efficiency values of 4.1 × 103%, 1.5 × 103%, 1.9 × 102%, and 9.9 ×101%, respectively. Unprecedentedly, from the successive responsivity measurements, an ionization transition level of an in-gap defect in ZTO has been proposed to be peaking at ∼2.3 eV below the conduction band causing the visible light sensitivity. This simple ZTO thin film-based UVB to visible broad-band photodetection is very promising for future optoelectronic applications.