Strain-induced Lateral-layer Ordering Research Articles

Formation of multiple quantum wires by strain-induced lateral-layer ordering process

Quantum wire heterostructures have been grown in situ using gas source molecular beam epitaxy. Lateral composition variation was achieved in the Ga x In 1- x P material system via a strain-induced lateral-layer ordering process occurring spontaneously when (GaP) n/(InP) n short-period superlattices are grown on (100)-oriented on-axis GaAs substrates. This results in a quasi-periodic modulation of the Ga x In 1- x P composition along the [110] direction with a periodicity of 95 °A. Thin (≈200°A) layers of these laterally ordered regions imbedded between bulk lattice-matched Ga 0.51In 0.49P epilayers in the longitudinal direction form quantum wire arrays. The formation of multiple quantum wires is confirmed by cross-sectional transmission electron microscopy. The Ga x In 1- x P multiple quantum wire heterostructure exhibits highly polarized photoluminescence spectra with peak intensity ratios of over 24 for the two orthogonal polarizations as a result of strain-induced lateral-layer ordering.

Formation of lateral quantum wells in vertical short-period superlattices by strain-induced lateral-layer ordering process

The lateral quantum wells formed in vertical (GaAs)n/(InAs)n and (GaP)n/(InP)n short-period superlattices (SPS) grown on nominally (100) InP and GaAs substrates, respectively, have been examined. The strain induced from the deviation of superlattice periodicity from na0 is the major driving force of the lateral modulation of the composition along the [110] direction, where the integer n is the number of monolayers of each binary compound within a period of SPS structure and a0 is the lattice constant of the substrate material. When the deviation of the superlattice periodicity from na0 is larger than ∼4%, both (GaAs)n/(InAs)n and (GaP)n/(InP)n ordered vertical SPS layers were found to have a lateral periodic modulation of composition with periodicities as small as ∼200 Å. This effect is enhanced when n was increased from 1 to 2.