Investigation of GaN-based avalanche photodiodes

Abstract

GaN-based avalanche photodiodes (APDs) have become of increased interest in the UV detection arenas. However, numerous material-, fabrication-, and design-related problems are exactly settled before GaN-based APDs can be commercialized. In this study, we, first, discussed recent development of the GaN-based APDs. Then front- and back-illumination (respectively realizing electron and hole initial impact-ionization) p-i-n heterostructure devices with various mesa diameters were fabricated. The device with a diameter of 40 μm exhibited a multiplication gain of ~680, at reverse bias of ~76 V corresponding to the magnitude of the electric field of ~ 3 MV/cm by experiment indicating and simulation verifying. To confirm the origin of dark current under different reverse bias, the dark current-voltage characteristic of various sized mesa devices were performed. The dark current could be linearly fitted to the device diameter (or circumference) implied that the surface leakage along the mesa sidewall was the dominant component of the dark current. At zero bias, the spectral peak responsivity reached ~ 0.14A/W for front illumination, and ~ 0.152A/W for back illumination at a wavelength of 358 nm. The positive breakdown voltage coefficient from the temperature-dependent current-voltage characteristics was 0.02 V/K.