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A complete dislocation analysis on a large number of grown-in dislocations was performed on wafers taken from three different semi-insulating liquid encapsulation Czochralski GaAs single crystals. By determining the Burgers vector, line direction, and habit plane of nearly 800 dislocations a decision could be made on dislocation type, dislocation generation, and multiplication mechanisms. Taking into account possible dislocation reactions between stress-induced glide systems all detected glide systems could be explained. The influence of post-growth annealing on both dislocations and arsenic precipitates was also investigated. Little effect was found on dislocations. Arsenic precipitates, however, showed a different distribution in size and significant effects on fine structure giving information on their nucleation and growth mechanisms.

The ac thin-film electroluminescence devices employing ZnS : Mn as the active medium exhibit a ’’memory effect’’ which in turn is related to filamentary luminescence. Under certain film preparation and device excitation conditions, it is found that the filaments exhibit a large scale cooperative motion. Spontaneously moving spirals and stripes have been observed under steady-state conditions. This paper describes the phenomena, and a thermal model for the observations is proposed.

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Three independent but complementary methods (OSL photoetching combined with etch rate profiling, spatially resolved PL and LST) were employed to Study the distribution of microdefects and electrically active centres in commercially available SI undoped. LEc-grown GaAs after different ingot-annealing treatments. A one-to-one correlation was obtained on comparing the microscale distribution of decoration precipitates (OPS), matrix precipitates (MPI) and microdefects (MMS) by the DSL and LST methods. Clustering of MPS is also revealed by PL intensity profiling and photoetch rate measurements. Two types of matrix microdefects are distinguishable by OSL photoetchlng In Samples after two-stage annealing. A high degree of homogeneity across the dislocation cells (after low-temperature and multiple annealing) was clearly revealed by a drastic decrease in the uniformity parameter (U) after DSL photoetching and by a significant decrease in the x intensity measured at the cell walls with respect to the cell interiors. Using the present results and recent data from the literature, an explanation of phase transitions during ingot annealing is proposed. This is based on the assumption that the final properties and structures after annealing are the result of two competitive processes: (i) formation of decoration and matrix microdefects; (ii) generation of electrically active point defects (clusters), presumably EL2