Ultraviolet radiation photodetectors based on structures consisting of a metal and a wide-bandgap semiconductor

Abstract

Recently, much attention has been given to measuring and monitoring ultraviolet radiation from the Sun and artificial sources. Detectors based on various wide-bandgap surface-barrier structures, which are characterized by a linear dependence of the photocurrent on incident power density in the range of 10−2–103 W/m2 and can record various kinds of ultraviolet radiation, are described. For example, GaP detectors with a UFS-6 filter have a spectral photosensitivity range corresponding to that of solar ultraviolet radiation on the Earth’s surface. The spectral sensitivity of 4H-SiC surface-barrier photodetectors corresponds to the spectral curve of the bactericidal effect produced by ultraviolet radiation. A model has been developed for explaining the process of short-wavelength photoelectric conversion. According to this model, photogenerated electrons and holes can unite into hot excitons, being thus excluded from the photoelectric conversion process. The rise in quantum efficiency with increasing temperature, which has been established experimentally for photodetectors based on Schottky barriers, is attributed to the capture of photogenerated carriers by traps arising from fluctuations of the conduction and valence band edges, with subsequent thermal release of these carriers. These fluctuations are related to imperfections in the surface layer of the semiconductor, which is confirmed by the temperature independence of the quantum efficiency of photodetectors based on p-n structures.