GENERATION OF DEGRADATION DEFECTS, STACKING-FAULTS, AND MISFIT DISLOCATIONS IN ZNSE-BASED FILMS GROWN ON GAAS

Transmission electron microscopy is used to investigate the structure of the crystalline defects in degraded and undegraded ZnSe-based films /GaAs heterostructures. In degraded areas, dark line defects (DLDs) or iginate from the preexisting or grown-in defects (i.e., stacking fault s and misfit dislocations) during device operation and make the laser diode fail. From our observation, the nucleation of DLDs is based on t he initial emission of a mobile faulted defect from the preexisting gr own-in defects. Along the trace of the faulted defects, [100] dark lin e defects form. We also investigated the origins and mechanisms for th e generation of stacking faults and misfit dislocations. The generatio n of stacking faults is strongly related to the doping concentration, substrate surface stoichiometry, and growth mode of the films. The vac ancy contained Ga-Se interfacial layers are thought to be sources for the generation of Frank-type stacking faults. In addition, Shockley pa rtial dislocations form due to island coalescence of the ZnSxSe1-x/ZnS e epilayers on GaAs substrates. In situ electron beam heating studies were carried out to realize the mechanism of strain relaxation and for mation of 60 degrees-type misfit dislocations in the II-VI/GaAs interf ace from the dissociation of Frank-type partial dislocations. The gene ration of screw-type interfacial dislocations was also observed. This takes place by gliding the threading segments of the Shockley partial dislocations toward the ZnSxSe1-x/GaAs interface on {111}-type planes. (C) 1995 American Vacuum Society.