Time Decay and Temperature Dependence of Radiative Recombination in (Zn, O)-Doped GaP

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Abstract
To understand the kinetics of the radiative emission in (Zn, O)-doped GaP, primarily at room temperature, we have measured luminescence lifetimes using pulsed photoexcitation from argon and He–Ne lasers. Measurements of time decay and temperature dependences of the radiative emission have enabled us to identify the emission in the near infrared as resulting from transitions involving a bound electron at an oxygen site to a free hole in the valence band. Measurements of the temperature dependence of the decay times and the luminescence intensities of the exciton (red) and bound-electron to free-hole (infrared) emissions also substantiate the conclusions that nonradiative recombination paths exist out of the Zn–O complex and provide evidence for the existence of a nonradiative ``shunt path'' out of the conduction band. The bound electron to free-hole recombination out of oxygen is believed to be primarily radiative. For an annealed sample, the decay times of the exciton and bound-to-free transitions are measured to be 170 nsec and 11.2 μsec at 300°K. From the relative variation of the excitonic and bound electron to free-hole intensities and their decay times in annealed and quenched samples it is reaffirmed that on annealing the quantum efficiency of the exciton emission increases and, furthermore, concluded that on annealing the quantum efficiency of bound-electron to free-hole emission also increases. A study of these effects increases our understanding of the process of annealing. Finally a weak correlation between the external quantum efficiency of excitonic (red) emission and its decay times is established for optimally doped, solution-grown GaP.