A study of the dislocations in Si-doped GaAs comparing diluted Sirtl light etching, electron-beam-induced-current, and micro-Raman techniques

Impurity atmospheres around dislocations have been studied in n-type Si-doped liquid encapsulated Czochralski (LEC) GaAs substrates by micro-Raman spectroscopy, diluted Sirtl-like etching with light (DSL) method, and electron-beam-induced current (EBIC). A complete morphological study of the recombinative atmospheres revealed by photoetching was achieved by phase stepping microscopy (PSM), which is an optical interferometry technique allowing to obtain the surface topography with a high vertical resolution (in the nanometer range). The minority carrier diffusion length was measured by EBIC at different points of the atmospheres. Structural distortion at the regions surrounding the dislocation core were observed by micro-Raman spectroscopy. The carrier depletion depth and the recombination of the photogenerated carriers were also studied by Raman spectroscopy, obtaining a good agreement with the EBIC data and the photoetching rates. Impurity gettering and diffusion and defect reactions involving As interstitials are assumed to play a major role in the formation of the recombinative atmospheres.