Deep Ultraviolet Photodetector Based on Sulphur-Doped Cubic Boron Nitride Thin Film

Cubic boron nitride (c-BN) is a wide bandgap III-V compound semiconductor potentially useful for solar-blind photodetectors. This paper describes work on the use of Sulphur doping to adjust the bandgap of c-BN films prepared by plasma-enhanced chemical vapor deposition (PECVD). An S-doped c-BN film based metal-semiconductor-metal (MSM) solar-blind ultraviolet (SBUV) photodetector was successfully fabricated and its electro-optical properties were characterized. The photocurrent shows peak responsivity at 254nm with sharp cutoff wavelengths at 220 and 300 nm, respectively, which is appropriate for use in solar-blind detection. The maximum response reached 1.55×10-7 A/W/cm2 with a rejection ratio of more than three orders of magnitude. The high solar-blind region UV response could be attributed to the successful substitution of boron by Sulphur and the suppression of B vacancies. The experimental results show the same peak in response at around 254nm as is found in the theoretical analysis.