Critical thickness of GaAs/InGaAs and AlGaAs/GaAsP strained quantum wells grown by organometallic chemical vapor deposition

Abstract

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (hc) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In0.11Ga0.89As, in which the QW layers are under biaxialcompression, and Al0.35Ga0.65As/GaAs0.82P0.18, in which the QW layers are under biaxialtension. 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 exceededhc and have undergone partial relaxation are thermodynamically stable against further dislocation propagation.