Avalanche characteristics in thin GaN avalanche photodiodes

A Monte Carlo model using random ionization path lengths describing the carriers quantum transport in thin gallium nitride (GaN) avalanche photodiodes (APDs) for ultraviolet detection in industry is developed. This work simulated avalanche characteristics such as impact ionization coefficients, mean multiplication gain and excess noise factor of GaN APDs at 0.05 mu m, 0.1 mu m, 0.2 mu m and 0.3 mu m multiplication widths in an electric field. The model simulates higher electron impact ionization coefficients than that of the hole for an electric field greater than 4.04 MV cm(-1). Mean multiplication gain and excess noise factor are simulated based on the electric field dependent impact ionization coefficients. Our results show that electron-initiated multiplication gives higher multiplication gain and lower excess noise than hole-initiated multiplication for a multiplication width below 0.3 mu m. Devices with dead space in general give a lower excess noise. (C) 2019 The Japan Society of Applied Physics