Nonuniform photoluminescence intensity distribution on semi-insulating GaAs and effects of Cr and dislocations

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Abstract
The nonuniformity of semi-insulating GaAs is studied by the near-band-edge luminescence (PL) intensity profile along the diameter of circular wafers grown by the liquid encapsulated Czochralski technique. The shapes of the profiles depend on the location of the wafer in the ingots and on the density of Cr. Many sharp peaks are observed in the profiles of undoped and lightly Cr-doped ingots but are suppressed by heavy doping of Cr. PL intensity is enhanced in the region where dislocation density is high. This correlation is explained by the interaction between the dislocation and the nonradiative center.