Current Transport and Band Alignment Study of MoS₂/GaN and MoS₂/AlGaN Heterointerfaces for Broadband Photodetection Application

Abstract

Gallium nitride (GaN) and aluminium gallium nitride (AlGaN) are promising materials for optoelectronics because of their direct band gap and high electron mobility. However, their optical absorbance being limited to within the ultraviolet (UV) range constrains their deployment in broadband photodetectors. Here, we combine three-dimensional (3D) epitaxial GaN and AlGaN thin films with visible-spectrum active two-dimensional (2D) molybdenum disulphide (MoS2) to create a 2D/3D hybrid that is active across a broadband spectrum. The interfacial properties of 2D/3D heterojunctions are thoroughly investigated on an industrially compatible silicon platform where a staggered gap (type II) band structure leads to a rectifying heterojunction phenomenon. It is shown that the optical absorbance spectra can be broadened by several hundreds of nanometers using this hybrid approach. As a result, these heterostructures are promising to cover broadband photodetection from ultraviolet (UV)-A (UV-B) to visible solar spectrum, thereby enhancing the practical utility of GaN and its alloys.