The characterisation of the donors in GaAs epitaxial films by far-infrared photoconductive techniques

Abstract

The high sensitivity of photoconductive techniques is exploited to study the central cell structure on the extrinsic donor spectra of pure n-type epitaxial films of GaAs. Experiments with back-doped samples have enabled the chemical shifts of most of the common donors to be determined with some confidence. The residual contaminants are identified in material from different sources prepared without intentional doping by conventional vapour and liquid phase techniques and by the recently developed 'alkyl' vapour epitaxial process. Each growth process produces a different set of residual contaminants, but samples grown by the same technique in different laboratories have a very similar donor spectrum.