Directional carrier transport in micrometer-thick gallium oxide films for high-performance deep-ultraviolet photodetection

TL;DR

This paper demonstrates that controlling defect profiles in micrometer-thick gallium oxide films significantly enhances deep-ultraviolet photodetector performance by improving responsivity and response time through directional carrier transport.

Contribution

It introduces a method to optimize defect profiles in thick Ga2O3 films, achieving high responsivity and fast response in MSM photodetectors for DUV detection.

Findings

Over 18-fold increase in responsivity

Response time reduced to 123 ms

Photo-to-dark current ratio near 10^8

Abstract

Incorporating emerging ultrawide bandgap semiconductors with a metal-semiconductor-metal (MSM) architecture is highly desired for deep-ultraviolet (DUV) photodetection. However, synthesis-induced defects in semiconductors complicate the rational design of MSM DUV photodetectors due to their dual role as carrier donors and trap centers, leading to a commonly observed trade-off between responsivity and response time. Here, we demonstrate a simultaneous improvement of these two parameters in {\epsilon}-Ga2O3 MSM photodetectors by establishing a low-defect diffusion barrier for directional carrier transport. Specifically, using a micrometer thickness far exceeding its effective light absorption depth, the {\epsilon}-Ga2O3 MSM photodetector achieves over 18-fold enhancement of responsivity and simultaneous reduction of the response time, which exhibits a state-of-the-art photo-to-dark current ratio near 10^8, a superior responsivity of >1300 A/W, an ultrahigh detectivity of >10^16 Jones and a decay time of 123 ms. Combined depth-profile spectroscopic and microscopic analysis reveals the existence of a broad defective region near the lattice-mismatched interface followed by a more defect-free dark region, while the latter one serves as a diffusion barrier to assist frontward carrier transport for substantially enhancing the photodetector performance. This work reveals the critical role of the semiconductor defect profile in tuning carrier transport for fabricating high-performance MSM DUV photodetectors.