High resolution carrier temperature and lifetime topography of semi-insulating GaAs using spatially and spectrally resolved photoluminescence

Abstract

The temperature Te of photoexcited carriers in semi-insulating GaAs wafers is determined with high lateral resolution by topographic measurement of the spectrally selected band-to-band recombination luminescence intensity IPL. It is also calculated from a detailed balance between carrier excitation and recombination, taking into account optical phonon, electron-electron, piezoelectric, and acoustic phonon scattering processes. Comparison of the experimental and theoretical Te data yields the lifetime τ of the photoexcited carriers, which is thus obtained without time-resolved measurement. The lifetime results are corroborated by comparison of the measured and calculated dependence of Te on the laser excitation power. The relation between Te and τ for given excitation power allows for the generation of two-dimensional high-resolution lifetime topograms. The correlation with conventional IPL topograms is direct, duplicating the lateral cellular pattern with comparable fluctuation amplitude. From these properties, it is inferred that τ is dominantly determined by inhomogeneously distributed nonradiative recombination centers. Their concentration is low in the walls of the dislocation network and high in the interior of the cells. The statistical evaluation of Te topograms allows for an application-oriented comparison of the quality and homogeneity of GaAs wafers.