Micron-Thick Hexagonal Boron Nitride Crystalline Film for Vacuum Ultraviolet Photodetection with Improved Sensitivity and Spectral Response

Hexagonal boron nitride crystalline film with a thickness of 70 μm is deposited on a c-plane sapphire at 1700 °C by the chemical vapor deposition (CVD) method. In X-ray diffraction (XRD) characterizations, a peak of (002) is observed at 26.01° with the full width at half-maximum (FWHM) of 1.17°, and the c-axis lattice constant is estimated to be 6.84 Å. The characterization results of Raman and X-ray photoelectron spectroscopy further confirm the film's high quality. Based on the h-BN film, a vacuum ultraviolet (VUV) photodetector is further fabricated with a responsivity of 48.7 μA/W, exhibiting a photo-to-dark current ratio (PDCR) of more than 103 as well as an excellent spectral selectivity to short-wave ultraviolet irradiation. By analyzing the photoresponse process, the influence of different response mechanisms is explained, implying the photodetector's ability to respond quickly.