TEM in situ study of degradation mechanisms induced by temperature annealing and electron beam irradiation in a ZnSe/GaAs heterostructure

Transmission electron microscopy is used to investigate the microstructure evolution of a ZnSe/GaAs layer under the simultaneous influence of electron beam irradiation (in the range 1000-5000 A/m2) and specimen heating (in the range ambient-250 deg. C). Degradation of the layer is connected to the nucleation and growth of dislocation loops. At 150 deg. C, loops nucleate on pre-existing misfit dislocations lying in <3 1 0> directions by point defect accumulation consistent with a climb mechanism. At 250 deg. C, large zones of very tangled dislocations propagate rapidly mainly by climb under electron beam excitation leading to a complete degradation of the ZnSe layer. The elementary mechanisms involved in dislocation multiplication are enhanced by non-radiative recombination of electron hole pairs