Spatially resolved luminescence near dislocations in In-alloyed Czochralski-grown GaAs

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Abstract
Spatially resolved maps of the near-band-edge band-to-acceptor photoluminescence intensity near isolated dislocations in semi-insulating Czochralski-grown In-alloyed GaAs are presented and discussed. Bright rings ∼150 μm in radius surround 100 μm dark spots centered on dislocations. Far from dislocations the luminescence intensity is two to three orders of magnitude lower than in the rings surrounding dislocations. Spectra from bright and dark regions do not indicate a major difference in In content. The magnitude of the luminescence contrast suggests that it is the lifetime of free carriers rather than the concentration of acceptors involved in the luminescence that directly determines the amount of contrast. The lifetime of electrons may be controlled in turn by the concentration of the positive charge state of the defect causing EL2.