The photoplastic effect in GaAs, a model for device degradation phenomena

Photoplasticity in GaAs has been studied by microhardness tests performed at room temperature and followed by laser irradiation. It is shown that the two glide directions ‘110’ of the (100) plane are photoactivated in the case of n-type and semi-insulating materials while only one of these is photoactivated in the case of p-type materials. This is explained in terms of dislocation-related defects inducing non-radiative electronic recombination, as can be described by configuration-coordinate diagrams. Light irradiation of laser-like epitaxial heterostructures, whose active layer is p-type, has been studied by means of cathodoluminescence imaging. The sequence of formation of the dark-line defects (DLDs) is described and it is shown that the first DLDs correspond to a photoinduced dislocation glide in one of the ‘110’ directions. They appear in regions of the GaAs layers where inhomogeneous stresses are probably present. In p-type layers, this first degradation step is then followed by dislocation climb in the ‘100’ directions in order to release totally and homogeneously the local stresses, since the other glide direction cannot be photoinduced. The high point-defect density needed for such dislocation climb probably results from the previously developed dislocations which are ideally localized active point-defect sources.