Back-Illuminated GaN/AlGaN Solar-Blind Avalanche Photodiodes

The separate absorption and multiplication (SAM) GaN/AlGaN solar-blind avalanche photodiodes (APDs) integrated with the specific design of 1-D dual-periodic photonic crystal on the back of the sapphire substrate are investigated numerically. The calculated results show that the proposed APDs can increase significantly the avalanche gain compared with the conventional SAM AlGaN solar-blind APDs using GaN instead of AlGaN as the multiplication layer. The enhanced performance can be explained by the larger hole ionization coefficient in the multiplication layer, the higher hole injection efficiency, and the reduced total dark current in this APDs. Meanwhile, the cutoff wavelength of 282 nm is achieved due to the optical filter effect of 1-D dual-periodic photonic crystal.