Analysis of Impurity Distribution in Homoepitaxial n on n+ Films of GaAs. II

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Abstract
The nature and cause of a high‐resistivity region (i layer) at the interface of n‐type on bulk n+ have received the attention of many workers in the field. Our previous investigations of impurity distributions of n+ films on n+ bulk substrates by Direct Image Mass Analysis (DIMA) have correlated a high concentration of silicon with a high‐resistivity region at the interface. Further analysis of the impurity distribution in epitaxial layers grown on bulk substrates and epitaxial layers grown on buffer layers (epitaxial layers doped to the mid‐1017 cm−3 range) by vapor phase epitaxy and liquid phase epitaxy have been performed. The main conclusions of the present analysis are: (A) The buffer layer is effective in isolating the lightly doped n layer from segregated impurities at the buffer‐substrate interface. (B) Group I and Group II elements have a great affinity for surfaces. (C) Preliminary observations on impurity “clusters” indicate that complicated impurity interactions may be present in . (D) The occurrence of a high concentration of silicon at the interface of epitaxial is definitely established.