Radiative recombination efficiencies in Ga(As,P) : N and (In,Ga)P : N

Abstract

The recombination kinetic equations for a III‐V mixed crystal alloy containing isolated nitrogen impurities [e.g., Ga(As,P) : N and (In,Ga)P : N] and acceptor impurities are solved in steady state, and the internal quantum efficiency is calculated for compositions greater than that at the direct‐indirect crossover. The model which is considered treats three states of the nitrogen: neutral nitrogen, electrons bound to the nitrogen by a short‐range potential (i.e., the Koster‐Slater model), and hydrogenic excitons bound to the nitrogen. In addition, intervalley scattering is included. Because of the large densities of states of the indirect X minimum and the valence band, a simple appoximation is derived which is roughly valid for nitrogen and acceptor concentrations less than the corresponding densities of states associated with the X minimum and the valence band. From the short thermalization times for bound electrons and bound excitons, the roles of the X minimum in efficiently pumping electrons into the nitrogen level and of the valence band in supplying holes to the bound excitonic states are elucidated. In addition, the bound‐exciton radiative lifetime is found to be dominant in determining the composition dependence of the efficiency. The internal quantum efficiency for a large excitonic hole capture cross section is proportional to the product of the nitrogen and free‐hole concentrations and is in good agreement with light‐emitting‐diode experiments. These results emphasize the importance of nitrogen for light emission in these systems.