GaxIn1−xAs quantum wire heterostructures formed by strain-induced lateral-layer ordering

Abstract

GaxIn1−xAs quantum wire (QWR) arrays were grown on (100) on-axis InP substrates by single-step molecular-beam epitaxy. The QWRs were formed in situ in (GaAs)2/(InAs)2.2 short-period-superlattice (SPS) layers by the strain-induced lateral-layer ordering (SILO) process. An analysis of the cross-sectional and plan-view transmission electron microscopy images, photoluminescence peak energies, and polarization anisotropy has confirmed the QWR nature of these heterostructures. The SILO process occurs over a wide growth temperature range near 500 °C. However, both high and low growth temperatures result in a weaker lateral composition modulation. The strength of the lateral composition modulation is proportional to the total thickness of the SPS quantum-well layers, regardless of the thickness of the individual quantum well. In other words, the magnitude of composition modulation accumulates when growth proceeds. A strain-driven bulk solid-state diffusion model has been proven to be part of the driving force of the SILO process, in addition to a dynamic surface diffusion during growth.