DISLOCATION RELAXATION IN INASYP1-Y FILMS DEPOSITED ONTO (001) INP BYGAS-SOURCE MOLECULAR-BEAM EPITAXY

The strain relaxation of InAsyP1-y layers grown on (001) InP substrate s by gas-source molecular beam epitaxy was examined using transmission electron microscopy (TEM) and cathodoluminescence (CL) imaging. InAsy P1-y films with a thickness of 190 angstrom were prepared, systematica lly varying the As content from y=0.30 and 0.77, corresponding to a la ttice mismatch between 0.97% and 2.5%. Relaxation was anisotropic, wit h 60-degrees misfit dislocations lying predominantly along [110BAR], w ith a much lower density of dislocations along [110]. For y > 0.48, CL and plan-view TEM observations show slip traces which make angles of about +/- 40-degrees with the [110BAR] direction. These slip traces co rrespond to pure-screw dislocation segments (gliding on {111}) cross s lipping to glide on planes approximately parallel to {011}.