Multi-layer MoS2/GaN UV-Visible photodetector with observation of MoS2 band edge in spectral responsivity

TL;DR

This paper demonstrates a MoS2/GaN UV-visible photodetector with high spectral responsivity, revealing MoS2's band edge in spectral responsivity, and shows distinct spectral steps at UV and visible wavelengths.

Contribution

It introduces a novel multi-layer MoS2/GaN photodetector with high responsivity and observes MoS2's band edge in spectral response, advancing UV-visible photodetector technology.

Findings

Spectral responsivity steps at 365 nm and 685 nm observed.

Responsivity of 0.1 A/W at 365 nm, 33 A/W at 685 nm.

Photo-to-dark current ratio of ~4000 at 365 nm.

Abstract

We report on the demonstration of MoS2/GaN UV-visible photodetectors with high spectral responsivity both in UV and in visible regions as well as the observation of MoS2 band-edge in spectral responsivity. Multi-layer MoS2 flakes of thickness ~ 200 nm were exfoliated on epitaxial GaN-on-sapphire, followed by fabrication of detectors in a lateral Metal-Semiconductor-Metal (MSM) geometry with Ni/Au contacts which were insulated from the GaN layer underneath by Al2O3 dielectric. Devices exhibited distinct steps in spectral responsivity at 365 nm and at ~ 685 nm with a corresponding photo-to-dark current ratio of ~4000 and ~ 100 respectively. Responsivity of 0.1 A/W (at 10 V) was measured at 365 nm corresponding to GaN band edge, while the second band edge at ~ 685 nm is characterized by a spectral responsivity (SR) of ~ 33 A/W when accounted for the flake size, corresponding to the direct band gap at K point of multi-layer MoS2.