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Micro Raman spectroscopy was used in order to clarify dislocation-related effects in a GaAs sample Bridgemangrown from a slightly As-rich melt and doped with Si to achieve a free electron concentration of about 10'* c~n -~. The specific advantage of the Raman method is demonstrated by the direct observation of an increase in the carrier concentration in the vicinity of dislocations and by the detection of both crystalline and amorphous As in the dislocation core. A defect model is proposed, which is in agreement with results obtained by other methods such as high spatial resolution photoluminescence. The possibility of determining internal lattice distortions by means of Raman spectroscopy is discussed, but further systematic investigations are necessary to obtain reliable results.

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