MICRO-RAMAN STUDY OF DISLOCATIONS IN N-TYPE DOPED GAAS

Micro Raman spectroscopy was used in order to clarify dislocation-rela ted effects in a GaAs sample Bridgeman-grown from a slightly As-rich m elt and doped with Si to achieve a free electron concentration of abou t 10(-18) cm-3. The specific advantage of the Raman method is demonstr ated by the direct observation of an increase in the carrier concentra tion in the vicinity of dislocations and by the detection of both crys talline and amorphous As in the dislocation core. A defect model is pr oposed, which is in agreement with results obtained by other methods s uch as high spatial resolution photoluminescence. The possibility of d etermining internal lattice distortions by means of Raman spectroscopy is discussed, but further systematic investigations are necessary to obtain reliable results.