Recombination Kinetics of Electrons and Holes at Isoelectronic Impurities: GaP (Zn,O)

Abstract

A model describing the kinetics of electron and hole (exciton) recombination at isoelectronic impurities is presented. The model considers three separate occupation states for the isoelectronic center, i.e., empty, electron (hole) occupied, and exciton occupied As a result, it generalizes the conventional two-state Shockley-Read-Hall (SRH) model which cannot be applied to recombination at isoelectronic centers. A detailed analysis is given of the time-dependent behavior of the radiative recombination at iseolectronic centers. Included in the analysis are the effects of nonradiative Auger and thermalization process. It is shown that under steady-state conditions the recombination at isoelectronic centers can be described by the SRH model, provided that the temperature is not so high that thermalization of the electron (hole) occupied state becomes important. The radiative decay time is shown to depend at low temperatures on thermal dissociation of excitons bound to the centers, and at high temperatures on Auger processes and thermalization of the electron (hole) occupied state. Using the model, a good fit is obtained to the measured time decay of the red luminescence from p-type Zn,0-doped GaP for $0<T<\mathrm{}440\mathrm{}°$K. On the basis of the agreement between calculated and measured time-decay curves, values are given for the Auger parameters, and for the electron and hole-capture lifetimes of the isoelectronic Zn-O trap.