INVESTIGATIONS OF THE STRUCTURAL STABILITY OF HIGHLY STRAINED [(AL)GAIN]AS GA (PAS) MULTIPLE-QUANTUM WELLS/

The structural stability of highly strained [(Al)GaIn]As/Ga (PAs) stra ined layer superlattice (SLS) structures as a function of the average lattice mismatch is investigated. The SLS structures, grown by metalor ganic vapor-phase epitaxy, are studied by using high-resolution x-ray diffraction. The range of stable SLS structures obtained experimentall y is compared to a recent theoretical model assuming strain relaxation by formation of misfit dislocations [D. C. Houghton, M. Davies, and M . Dion, Appl. Phys. Lett. 64, 505 (1994)]. In particular, the influenc e of the surface migration length of the group-III species on the grow th surface is investigated by varying the Al concentration in the comp ressively strained [(Al)GaIn]As layers. Structurally stable [(Al)GaIn] As/Ga(PAs) SLS structures having a total layer thickness of 1 mu m and an average lattice mismatch of vp to (Delta d/d)(perpendicular to) = 1.2x10(-2) have been realized. These values exceed by far the values o f the misfit dislocation model. This behavior indicates that surface m orphology changes rather than misfit dislocation formation are the pri mary cause for the instability of highly strained SLSs. (C) 1996 Ameri can Institute of Physics.