Nonlinear optical effects in strain-induced laterally ordered(InP)2/(GaP<

Abstract

The nonlinear optical properties of a ͑InP͒ 2 /͑GaP͒ 2 bilayer superlattice structure have been examined with linearly polarized cathodoluminescence spectroscopy. Transmission electron microscopy showed a composition modulation with a period of ϳ800 Å along the ͓110͔ direction, which occurs spontaneously during the growth, resulting in coherently strained quantum wires. The strong excitation dependence of the polarization anisotropy and energy of excitonic luminescence from the quantum wires was found to be consistent with a band-filling model that is based on a k-p and two-dimensional quantum confinement calculation. ͓S0163-1829͑96͒51516-X͔ Nonlinear optical properties of III-V semiconductor nanostructures have attracted a great deal of interest, as they are important for applications in optical communications that involve switching, amplification, and signal processing. An important nonlinear optical property is the change in the emission of light ͑in energy, polarization, and intensity͒ that results from phase-space filling of carriers in one-and twodimensionally confined systems, i.e., quantum wells and wires. 1,2 This property is analogous to the Burstein-Moss band filling which occurs in bulk semiconductors and raises the energy of the unoccupied electron and hole states as the excitation intensity increases. As the dimensionality of the quantum confinement increases from one dimension ͑1D͒ to 2D, the narrowing of the density of states ͑DOS͒ will exhibit a lower excitation threshold for phase-space filling, thereby yielding potentially enhanced nonlinear optical effects. Recently, quantum wires have been fabricated by a straininduced lateral ordering ͑SILO͒ process which occurs spontaneously when (GaP) n /(InP) n and (GaAs) n /(InAs) n shortperiod superlattices are grown on GaAs͑001͒ and InP͑001͒, respectively. 3-7 Previous studies involving transmission electron microscopy ͑TEM͒ and optical measurements such as photoluminescence, electroluminescence, and photoreflectance have shown evidence supporting the existence of quantum wires due to quantum confinement along both the growth direction and the composition modulation direction. 5-8 However, the nature of phase-space filling and the concomitant influence on the polarization properties in these systems have yet to be investigated thoroughly. In this study, we examine the nonlinear optical properties of a ͑InP͒ 2 /͑GaP͒ 2 bilayer superlattice ͑BSL͒ structure using a linearly polarized cathodoluminescence ͑LPCL͒ technique. We demonstrate the existence of an interesting excitation-and temperature-dependent polarization anisotropy in luminescence coming from the SILO quantum wires. A theoretical simulation of the band-filling, luminescence energy shifts and polarization anisotropy changes was performed for the SILO quantum wires using a k-p band-structure calculation, which takes the coherency strain and 2D quantum confine-ment into account, and is compared with the experimental results. Evidence for these strong nonlinear optical effects is a cornerstone in ...

Linear and second-order optical response of III-V monolayer superlattices

“…20 The major theoretical work in this direction was done by Ghahramani et al 53,54,55,56 They used the effective-medium-model (EMM) to determine the linear and nonlinear optical properties of (GaAs) n /(GaP) n , (Si) n /(Ge) n and (GaAs) n /(AlAs) m SLs. They also employed the non-self-consistent linear-combination-of-Gaussian-orbitals (LCGO) method within the LDA to calculate the band structures and optical properties of these compounds.…”

“…14 InP/GaP, being one of the material combinations which spontaneously constructs the SL under specific conditions, has been subject to numerous experimental works 15,16,17 including cathodoluminescence experiments 18,19,20 and studies on the influence of pressure, SL period and barrier thickness 21,22,23 on the optical transitions. Likewise GaAs/GaP 24,25 and GaAs/AlAs 26,27,28,29,30,31,32 have also been extensively investigated in the past.…”

Systematic study of Ga1−xInxAs self-assembled quantum wires with varying interfacial strain relaxation

“…The k · p model is the most popular one for treating electronic structures of semiconductor quantum wells or superlattices. However, when applied to complex structures such as self-assembled quantum wires [4][5][6][7][8][9] or quantum dots [13,18,19], the method becomes very cumbersome if one wish to implement the correct boundary conditions that take into account the differences in k · p band parameters for different materials involved. EBOM is free of this problem, since different material parameters are used at different atomic sites in a natural way.…”

“…[8][9][10] In these calculations the SPS region is modeled by a Ga x In 1−x As alloy with a lateral modulation of the composition x. Although these calculations can explain the QWR band gap and optical anisotropy qualitatively, it does not take into account the detailed SPS structure and the microscopic strain distribution.…”

Time-resolved cathodoluminescence study of carrier relaxation in strained (InP)2/(GaP)2 quantum wires

“…One important nonlinear optical property is the change in the emission of light ͑in energy, polarization, and intensity͒ that results from phasespace filling of carriers. 8 In this letter, we examine the nonlinear optical effects and carrier relaxation kinetics of ͑InP͒ 2 /͑GaP͒ 2 QWR samples using time-resolved CL. In particular, we examine the extent to which defects and deviations from ideal QWR ordering will alter the optical properties.…”