Defect Engineering for Modulating the Trap States in Two-dimensional Photoconductor

TL;DR

This paper demonstrates defect engineering in two-dimensional ReS2 to modulate trap states, significantly improving photodetector response time and detectivity by molecule decoration.

Contribution

It introduces a method to fill deep trap states in ReS2 using molecule decoration, enhancing device speed and sensitivity.

Findings

Deep traps are filled by Protoporphyrin molecules.

Response time is reduced by orders of magnitude.

Detectivity is enhanced to ~1.89 x 10^13 Jones.

Abstract

Defect induced trap states are essential in determining the performance of semiconductor photodetectors. The de-trap time of carriers from a deep trap could be prolonged by several orders of magnitude as compared to shallow trap, resulting in additional decay/response time of the device. Here, we demonstrate that the trap states in two-dimensional ReS2 could be efficiently modulated by defect engineering through molecule decoration. The deep traps that greatly prolong the response time could be mostly filled by Protoporphyrin (H2PP) molecules. At the same time, carrier recombination and shallow traps would in-turn play dominant roles in determining the decay time of the device, which can be several orders of magnitude faster than the as-prepared device. Moreover, the specific detectivity of the device is enhanced (as high as ~1.89 x 10^13 Jones) due to the significant reduction of dark current through charge transfer between ReS2 and molecules. Defect engineering of trap states therefore provides a solution to achieve photodetectors with both high responsivity and fast response.