Metastability in the Matthews-Blakeslee mechanism for semiconductor film relaxation

摘要

Experimental evidence has been obtained for GaAs/Ge which demonstrates the high metastability of films of thickness t_c far above the critical thickness determined by the Matthews-Blakeslee model for relaxation in semiconductors. In addition, a dislocation blocking mechanism as describe by the Freund model has been found. Both are related to misfit behaviour and misfit dislocation (MD) glide with temperature. It is shown that one has to take into account the possibility that the MDs do not lie entirely in the glide planes and that the mobility of point defects needs to be considered to explain their development. The movement of MDs would be controlled by a "critical length' that actually lies in the slide plane and it is this thickness that must be compared with the critical value t_c rather than the whole layer thickness t_F.