Transmission electron microscopy was used to investigate the structures of crystalline defects in degraded and non-degraded ZnSe-based films on GaAs heterostructures. In degraded areas, dark-line defects originated from pre-existing or grown-in defects such as stacking faults and misfit dislocations. It was found that the nucleation of dark-line defects was based upon the initial emission of a mobile faulted defect from the pre-existing grown-in defects. Dark-line defects of [100]-type formed along the trace of the faulted defects. The origins and mechanisms of the generation of stacking faults and misfit dislocations were also investigated. The generation of stacking faults was strongly related to the dopant concentration, substrate surface stoichiometry, and the growth mode of the films. The vacancy-containing Ga-Se interfacial layers were thought to be sources for the generation of Frank-type stacking faults. In addition, Shockley partial dislocations formed due to the island coalescence of ZnSSe/ZnSe epilayers on GaAs substrates. Electron-beam heating was used to study strain relaxation and the formation of 60-type misfit dislocations, in the II-VI GaAs interface, via the dissociation of Frank-type partial dislocations. The generation of screw-type interfacial dislocations was also observed. This occurred via the gliding of threading segments of the Shockley partial dislocations towards the ZnSSe/GaAs interface on {111}-type planes.

L.H.Kuo, L.Salamanca-Riba, B.J.Wu, G.M.Haugen, J.M.DePuydt, G.Hofler, H.Cheng: Journal of Vacuum Science and Technology B, 1995, 13[4], 1694-704