Performance comparison of front- and back-illuminated modes of the AlGaN-based p-i-n solar-blind ultraviolet photodetectors

Abstract

The authors report the comparison of front- and back-illuminated mode operations of Al0.4Ga0.6N positive-intrinsic-negative solar-blind photodetectors (PDs) grown on the double-side polished sapphire substrates by metalorganic chemical vapor deposition. It is shown that the responsivity in back-illumination mode of fabricated PDs can be almost three times as that in front-illumination mode under the same reverse bias. In addition, a wide spectral response between 300 nm and 370 nm is observed, which is not expected for solar-blind PDs in both illumination modes, while the PDs in back-illumination mode have a stronger ability to restrain the long-wavelength response, showing larger solar-blind/ultraviolet rejection ratio than front-illumination mode. The reasons for the performance differences are discussed.