Sulfurization engineering of single-zone CVD vertical and horizontal MoS₂ on p-GaN heterostructures for self-powered UV photodetectors

Molybdenum disulfide (MoS₂) has been attracting considerable attention due to its excellent electrical and optical properties. We successfully grew high-quality, large-area and uniform few-layer (FL)-MoS₂ on p-doped gallium nitride (p-GaN) using a simplified sulfurization technique by the single-zone CVD of a Mo seed layer via E-beam evaporation. Tuning the sulfurization parameters, namely temperature and duration, has been discovered to be an effective strategy for improving MoS₂ orientation (horizontally aligned and vertically aligned) and quality, which affects photodetector (PD) performance. The increase in the sulfurization temperature to 850 °C results in improved structural quality and crystallite size. However, a prolonged sulfurization duration of 60 minutes caused the degradation of the film quality. The close lattice match between p-GaN and MoS₂ contributes to the excellent quality growth of deposited MoS₂. Following this, an n-MoS₂/p-GaN heterostructure PD was successfully built by a MoS₂ position-selectivity method. We report a highly sensitive and self-powered GaN/MoS₂ p-n heterojunction PD with a relatively high responsivity of 14.3 A W⁻¹, a high specific detectivity of 1.12 × 10¹³ Jones, and a fast response speed of 8.3/13.4 μs (20 kHz) under a UV light of 355 nm at zero-bias voltage. Our PD exhibits superior performance to that of the previously reported MoS₂/GaN p-n PD. Our findings suggest a more efficient and straightforward approach to building high-performance self-powered UV PDs.