Recent developments in the study of bulk GaAs properties by electron microscopy

Recent developments in the assessment of the properties of bulk GaAs crystals by SEM--EBIC and TEM are presented. The capability of EBIC of giving the majority carrier (dopant) concentration with a micron-scale spatial resolution is used to provide information on the electrical parameters of the large impurity atmospheres and gettering regions surrounding the dislocations in Si-doped LEC GaAs. Information on the impurities and point defects in these impurity atmospheres can thus be obtained. Application of EBIC to the determination of dopant density at growth striations is also discussed. The use ofTEM to the study of the nature of microdefects in as-grown as well as implanted crystals is shown. These microdefects turn out to be either dislocation loops or precipitates depending on the growth and/or processing conditions. The point defects, vacancies or interstitials, at their origin are also established. This also allows to explain the formation of surface microroughness that sometimes appears in GaAs after wet chemical etchings.