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Spatially Resolved Thermodynamics of the Partially Ionized Exciton Gas in GaAs
S Bieker1, T Henn1, T Kiessling1
1Physikalisches Institut (EP3) der Universität Würzburg, 97074 Würzburg, Germany.
Abstract:
We report on the observation of macroscopic free exciton photoluminescence (PL) rings that appear in spatially resolved PL images obtained on a high purity GaAs sample. We demonstrate that a spatial temperature gradient in the photocarrier system, which is due to nonresonant optical excitation, locally modifies the population balance between free excitons and the uncorrelated electron-hole plasma described by the Saha equation and accounts for the experimentally observed nontrivial PL profiles. The exciton ring formation is a particularly instructive manifestation of the spatially dependent thermodynamics of a partially ionized exciton gas in a bulk semiconductor.
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