ROLE OF SUBSTRATE THREADING DISLOCATION DENSITY IN RELAXATION OF HIGHLY STRAINED INGAAS/GAAS QUANTUM-WELL STRUCTURES

Structures with highly strained InGaAs/GaAs single quantum wells have been grown on GaAs substrates with KOH etch pit densities from ∼1000 to ∼45 000 cm-2. These structures were characterized by photoluminescence microscopy and 77 K Hall measurements to determine the extent to which the substrate threading dislocation density affects the misfit dislocation density at the quantum well interfaces. For well thicknesses near or below the Matthews-Blakeslee critical thickness, similar results are obtained for substrates of different dislocation density. However, for metastable structures significantly above the critical thickness, the misfit dislocation density is a sensitive function of the substrate quality.