High-Temperature Annealing-Assisted High-Quality sp 2 -BN Film by MOCVD for Vacuum Ultraviolet Detectors

All uniform and continuous wafer-scale sp 2 -hybridized boron nitride (sp 2 -BN) is one of the most promising candidate materials for vacuum ultraviolet photodetectors (VUV PDs). However, the fabrication of large-area, high-efficiency sp 2 -BN VUV PDs remains challenging. This study systematically investigates the role of high-temperature annealing-assisted metal–organic chemical vapor deposition (MOCVD) in enhancing thin-film quality and device performance. Through optimized annealing treatment, we achieved significant improvements in the crystalline uniformity of sp 2 -BN films and reduced dislocation density. Raman, FTIR, and XRD analyses consistently showed a narrowed full-width-at-half-maximum (FWHM) of characteristic peaks, while TEM cross-sectional imaging confirmed enhanced structural ordering. Mechanistic studies revealed that during annealing, nitridation of the sapphire substrate generated AlN interlayers, which guided the epitaxial rearrangement of BN molecules along the AlN crystallographic planes, thereby promoting defect annihilation. Device characterization demonstrated remarkable performance enhancements: response time (τ r /τ d ) decreased from 356.16/142.27 ms to 39.34/41.34 ms, responsivity increased by 193% to 0.79 mA/W, and detectivity improved by 267% to 3.45 × 10 10 Jones. This work establishes high-temperature annealing-assisted MOCVD as an effective strategy for optimizing sp 2 -BN VUV PDs, providing a viable pathway for advanced ultraviolet detection applications.