Self-Powered, Highly Sensitive, High Speed Photodetection Using ITO/WSe2/SnSe2 Vertical Heterojunction

TL;DR

This paper presents a self-powered, high-speed, highly sensitive photodetector based on an ITO/WSe2/SnSe2 heterojunction, demonstrating significant improvements in responsivity, response time, and stability against environmental effects.

Contribution

The study introduces a novel vertical heterojunction device with controlled charge transfer, achieving high responsivity and fast response while maintaining stability and self-powered operation.

Findings

Responsivity exceeds 1100 A/W.

Response time is approximately 10 microseconds.

Device exhibits stable, repeatable performance over many cycles.

Abstract

Two dimensional transition metal di-chalcogenides (TMDCs) are promising candidates for ultra-low intensity photodetection. However, the performance of these photodetectors is usually limited by ambience induced rapid performance degradation and long lived charge trapping induced slow response with a large persistent photocurrent when the light source is switched off. Here we demonstrate an indium tin oxide (ITO)/WSe$_2$/SnSe$_2$ based vertical double heterojunction photoconductive device where the photo-excited hole is confined in the double barrier quantum well, whereas the photo-excited electron can be transferred to either the ITO or the SnSe$_2$ layer in a controlled manner. The intrinsically short transit time of the photoelectrons in the vertical double heterojunction helps us to achieve high responsivity in excess of $1100$ A/W and fast transient response time on the order of $10$ $\mu$s. A large built-in field in the WSe$_2$ sandwich layer results in photodetection at zero external bias allowing a self-powered operation mode. The encapsulation from top and bottom protects the photo-active WSe$_2$ layer from ambience induced detrimental effects and substrate induced trapping effects helping us to achieve repeatable characteristics over many cycles.