Study of Wasted Space Effect in Avalanche Photodiodes: A New Look at the Size-Dependent Impact Ionization Properties under Submicron Scale

Abstract

Impact ionization is one of the most important behaviors for carrier transport in high-field region. In this paper, we study the size-dependent impact ionization coefficients induced by the distance that the carriers have to travel to leave out of the terminal of the multiplication layer after the last impact ionization event, which is defined as the “wasted space”. Monte Carlo method is carried out to calculate the size-dependent impact ionization coefficients under submicron scale, and to investigate the effect of wasted space. The conventional model of mean multiplication gain in avalanche photodiodes (APDs) is revised with the adoption of size-dependent impact ionization coefficients, and a good agreement is achieved in the device characteristics of multiplication gain of InP-based APD devices.