Engineering Vacancies in Bi2S3 yields sub-Bandgap Photoresponse and highly sensitive Short-Wave Infrared Photodetectors

TL;DR

This paper demonstrates how engineering sulphur vacancies in Bi2S3 can create sub-bandgap photoresponse for highly sensitive, fast, and broadband short-wave infrared photodetectors, with improved response times and spectral coverage.

Contribution

It introduces a chemical treatment method to enhance the speed of sulphur vacancy-based detectors without losing infrared spectral coverage, and provides new insights into vacancy-induced electronic structure modifications.

Findings

Sulphur vacancies enable sub-bandgap photoresponse in Bi2S3.

Chemical treatment accelerates detector response to ~10 ms.

Detectors achieve high D* values of 10^15 Jones in visible-near IR.

Abstract

Defects play an important role in tailoring the optoelectronic properties of materials. Here we demonstrate that sulphur vacancies are able to engineer sub-band photoresponse into the short-wave infrared range due to formation of in-gap states in Bi2S3 single crystals supported by density functional (DF) calculations. Sulfurization and subsequent refill of the vacancies results in faster response but limits the spectral range to the near infrared as determined by the bandgap of Bi2S3. A facile chemical treatment is then explored to accelerate the speed of sulphur deficient (SD)-based detectors on the order of 10 ms without sacrificing its spectral coverage into the infrared, while holding a high D* close to 10^15 Jones in the visible-near infrared range and 10^12 Jones at 1.6 um. This work also provides new insights into the role sulphur vacancies play on the electronic structure and, as a result, into sub-bandgap photoresponse enabling ultrasensitive, fast and broadband photodetectors.