The effects of majority carrier diffusion on the minority carrier radiative lifetime in thin layer surface free GaAs/AlGaAs structures

Abstract

It has been recently reported that the minority carrier radiative lifetime in thin layers sandwiched between degenerately doped barrier regions or heterojunction barriers is much reduced by the diffusion of majority carriers into the active layer from the barrier regions. We show here that the radiative lifetime is determined by the average majority carrier concentration which is dependent on active layer thickness and may be significantly higher than the dopant concentration in this layer. Our experimental results are in close agreement with this model. We have simulated a number of structures where the minority carriers are confined by either homojunctions or heterojunctions and have derived the radiative lifetime as a function of active layer thickness. This dependence of radiative lifetime on layer thickness is not embraced in the analysis normally used for example in interface studies but is shown to have a significant effect on the interpretation of results obtained from measurements of interface recombination velocity leading to erroneous conclusions if not taken into account.