Strain-Related Excitonic In-Plane Optical Anisotropy in (100) InGaAs/InAlAs/InP MQW

Strained (x=0.48) and lattice-matched (x=0.53) In x Ga l-x As/InAlAs/InP (100) MQWs have been investigated by photoreflectance. In the strained sample the relative intensities of the light-hole and heavy-hole excitonic transitions is different for the two different polarizations of the incident light parallel and perpendicular to the ]0-1-1 ] direction. This polarization anisotropy is explained in terms of the spontaneous formation of “quantum wires” and the presence of anisotropic strain due to spinodal-like phase decomposition of the InGaAs alloy in In-rich and Ga-rich regions.