Electron-beam-induced current and photoetching investigations of dislocations and impurity atmospheres in n-type liquid-encapsulated Czochralski GaAs

Typical defects in n-type liquid-encapsulated Czochralski GaAs, i.e., grown-in dislocations and grown-in and then stress-induced glide (GS) dislocations have been studied by electron-beaminduced current (EBIC) and diluted Sirtl-like etching with light (DSL photoetching). The study of GS dislocations was possible because both EBIC and DSL can reveal the recombinative traces left behind the moving dislocations. Grown-in dislocations and the ending points of GS dislocations exhibit a central feature more recombinative than the external atmosphere. No such central feature has been detected at the starting points of the GS dislocations. A model for the formation of the impurity atmospheres in the GS defects has been put forward. By quantitative EBIC measurements performed right in the impurity atmospheres (5-20 micron in size) around dislocations, the local space-charge region width of the EBIC Schottky diode was determined. Information on the net ionized impurity concentration in the atmospheres could thus be obtained. It has been established that silicon (dopant) autocompensation along with the gettering of other unknown impurities and point defect reactions probably involving arsenic interstitials are important features of the atmospheres.