Hochauflösende Topographie der Ladungsträger-Lebensdauer und -Temperatur von GaAs mittels Photolumineszenz

: Wang, Z.M.; Windscheif, J.; As, D.J.; Jantz, W.

Abstract
The temperature Tsube 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 IsubPL. 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 Tsube data yields the lifetime Tau 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 Tsube on the laser excitation power. The relation between Tsube and Tau for given excitation power allows for the generation of two-dimensional high-resolution lifetime topograms. The correlation with conventional IsubPL topograms is direct, duplicating the lateral cellular pattern with comparab le fluctuation amplitude. From these properties, it is inferred that Tau 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 Tsube topograms allows for an application-oriented comparison of the quality and homogeneity of GaAs wafers.