The Elimination of Misfit Dislocations at Mismatched InGaAs/GaAs Interfaces by a Reduction in Growth Area.

To investigate the effect of growth area on interface dislocation density in strained-layer epitaxy, we have fabricated 2-microns high mesas of varying lateral dimensions in (001) GaAs substrates with dislocation densities of 1.5x10 sup 5, 10 sup 4, and 10 sup 2 cm sup (-2). 3500 and 7000angstroms thick In sub (0.05) Ga sub (0.95) As layers, corresponding to approximately 5, 10, and 11 times the critical layer thickness as measured for large area samples, were then deposited by molecular beam epitaxy. For the 3500angstroms layers, we find that the linear interface dislocation density decreases from much greater than 5000 cm sup (-1) to less than 800 cm sup (-1) for mesas as large as 100microns. Dispite the doubling in epilayer thickness, the 7000angstroms layers posses linear interface dislocation densities less than 1500 cm sup (-1) for mesas as large as 100microns. Examination of the dependence of linear interface dislocation on mesa size reveals which nucleation sources are active.