Metal-organic chemical vapor deposition-grown wafer-scale hexagonal boron nitride for high-performance deep ultraviolet photodetectors

The large-area epitaxial growth of wafer-scale hexagonal boron nitride (h-BN) with a uniform surface and high crystalline quality is crucial for the fabrication and application of h-BN-based two-dimensional (2D) material devices. We investigate the influence of the V/III ratio on the crystal quality of h-BN by varying the triethylboron flow rate in metal-organic chemical vapor deposition. The results indicate that a lower V/III ratio enhances boron atom mobility, facilitating the lateral growth of h-BN, but too low V/III ratio will lead to a high concentration of carbon impurity doping. By optimizing the V/III ratio, we successfully achieve the growth of h-BN films on 2-in. sapphire substrate, with a particle-free surface, low impurity concentrations, and high crystalline quality. Based on high-quality h-BN, a deep ultraviolet photodetector is fabricated, demonstrating excellent response under 193 nm illumination. At 50 V and a light power density of 15.95 μW/mm2, the detector achieves a responsivity of 0.72 mA/W, a specific detectivity of 9.53×1011 Jones, and an on-off ratio of 103, with a response time in the millisecond range. We optimize the growth conditions for high-quality h-BN and realize the fabrication of optoelectronic devices, thereby paving the way for future wafer-scale 2D semiconductor electronic devices.