Substrate-dependent growth and optoelectronic properties of sputtered hexagonal boron nitride films

Abstract

Boron nitride films are deposited on sapphire substrates with miscut angles (C-plane toward M-direction, 0.1°–4.0°) using radio frequency magnetron sputtering. The deposited films exhibit the characteristic hexagonal boron nitride (h-BN) phase with smooth, dense, and continuous surface morphology. Increasing the substrate miscut angle leads to a progressive deviation of the absorption edge and optical bandgap from those of ideal single-crystalline h-BN. Raman spectroscopy reveals a redshift and broadening of the E2g vibrational mode with increasing miscut, indicating reduced crystallinity and enhanced internal stress. The h-BN film grown on the substrate with a miscut angle of 0.1° shows the most desirable characteristics, including a bandgap of 5.59 eV, minimal residual stress, and the narrowest E2g peak. Metal–semiconductor–metal photodetectors fabricated from the optimized h-BN film demonstrates excellent performance, achieving a photo-to-dark ratio of 217 and a responsivity of 8240 μA/W at 20 V bias. These findings elucidate the influence of substrate miscut on the structural and functional properties of sputtered h-BN films, offering guidance for the controlled growth of high-performance BN-based optoelectronic devices.