Cathodoluminescence measurements of the minority-carrier lifetime in semiconductors

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Abstract
Detailed calculations of the cathodoluminescence decay after an excitation pulse are developed; the generation function, the carrier diffusion, the surface recombination, the self-absorption, and the excitation-pulse duration are taken into account. It is demonstrated that the surface recombination leads to a nonexponential region at the beginning of the decay when short excitation pulses are used. This effect disappears with longer pulses. It can be used in order to determine separately the surface recombination velocity and the true bulk lifetime of the carriers. Nomograms are given which permit this determination without further calculation. The influence of the pulse duration on the form of the cathodoluminescence decay has been experimentally verified in GaP. The surface recombination velocities and the lifetimes in many samples have been deduced. Finally, it appears that this method provides a simple means of determining the minority-carrier lifetime in semiconductors.