Synthesis of MoS2 Layers on GaN Using Ammonium Tetrathiomolybdate for Heterojunction Device Applications

Abstract

2D materials such as molybdenum sulfide (MoS2) integrated with conventional semiconductors lead to the fabrication of novel heterojunctions with pivotal electrical and optoelectronic properties. Herein, an approach is reported which addresses the growth of MoS2 crystals on the lattice‐matched Ga–polar gallium nitride (GaN) wafer using ammonium tetrathiomolybdate (ATM) as a precursor in a chemical vapor deposition (CVD) process, instead of using the molybdenum‐oxide‐based precursors. Unidirectional triangular MoS2 crystals and continuous film are obtained on the free‐standing Ga–polar GaN substrate. Further, the interface quality of the as‐synthesized MoS2 crystals and GaN wafer is explored by X‐ray photoelectron spectroscopy. It is observed that a good quality interface can be obtained by using the ammonia‐containing ATM precursor, where the surface oxygen at the interface is significantly less. A heterojunction device is fabricated with the synthesized MoS2 layer on GaN, showing excellent rectifying diode characteristics and a photovoltaic action with light illumination. This study reveals the suitability of the ammonia‐containing ATM precursor for the growth of MoS2 crystals on GaN in the CVD process to obtain a suitable heterostructure for device applications.