CRITICAL THICKNESS OF GAAS/INGAAS AND ALGAAS/GAASP STRAINED QUANTUM-WELLS GROWN BY ORGANOMETALLIC CHEMICAL VAPOR-DEPOSITION

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (h c) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In0.11Ga0.89As, in which the QW layers are under biaxial compression, and Al0.35Ga0.65As/GaAs0.82P0.18, in which the QW layers are under biaxial tension. Samples were grown by atmospheric pressure organometallic chemical vapor deposition, and characterized by low-temperature photoluminescence (PL), x-ray diffraction, optical microscopy, and Hall measurements. For both material systems, the observed onset of dislocation formation agrees well with the force-balance model assuming a double-kink mechanism. However, overall results indicate that the relaxation is inhomogeneous. Annealing at 800-850° C had no significant effect on the PL spectra, signifying that even layers that have exceeded h c and have undergone partial relaxation are thermodynamically stable against further dislocation propagation. © 1990 AIME.