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A systematic theoretical study of the electronic and optical properties of Ga[sub 1-x]In[sub x]As self-assembled quantum wires (QWRs) made of short-period superlattices with strain-induced lateral ordering is presented. The theory is based on the effective bond-orbital model combined with a valence-force-field (VFF) model. Valence-band anisotropy, band mixing, and effects due to local strain distribution at the atomistic level are all taken into account. Several structure models with varying degrees of alloy mixing for lateral modulation are considered. A VFF model is used to find the equilibrium atomic positions in the QWR structure by minimizing the lattice energy. The strain tensor at each atomic (In or Ga) site is then obtained and included in the calculation of electronic states and optical properties. It is found that different local arrangement of atoms leads to very different strain distribution, which in turn alters the optical properties. In particular, we find that in model structures with thick capping layer the electrons and holes are confined in the Ga-rich region and the optical anisotropy can be reversed due to the variation of lateral alloy mixing, while for model structures with thin capping layer the electrons and holes are confined in the In-rich region, and the optical anisotropy is much less sensitive to the lateral alloy mixing. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Deals with a study which theoretically examined the changes in index refraction of semiconductor superlattices due to electric field. Use of a parabolic band effective-mass approximation; Area in which excitonic effects are considered; Factors that have provided advantages over bulk semiconductors.

Presents a study which examined the transient behaviors of the optical bistability (OB) and degenerate four-wave mixing in semiconductor superlattices. Dispersive OB; Absorbtive OB; General solution of the degenerate four-wave mixing.

Analyzes the nonlinear optical properties of semiconductor superlattices. Description of the two-band model for semiconductor superlattices; Details on the conduction-band nonparabolicity effect; Information on the photoexcited plasma effect.

Presents a study that examined a linear and two-photon absorptions of silicon-germanium strained-layer superlattices. Theoretical model; Band structures; Optical matrix elements; Discussion of linear and two-photon absorption.

Presents information on a study which analyzed linear and two-photon absorption spectra of HgTe/CdTe superlattices with rectangular and sawtooth potential profiles. Use of the effective bond orbital model to calculate the band structures; Examination of the validity of the procedure for incorporating the temperature dependence; Calculation of optical matrix element.

Reports on the theoretical studies of the band structures, photoabsorption, electro-optic coefficient and second order susceptibility (X²) of Hg[subt]-[subx]Cd[subx]Te sawtooth superlattices. Details on supelattices made with HgTE and CdTe; Discussion on band structures; Description of electro-optic effect in semiconductor superlattices.

The effect of interdiffusion on the band gap of the HgTe-CdTe superlattice is calculated. Two simple models of the form of the interdiffusion are assumed: linear compositional grading, or shrinkage of HgTe layer widths due to Hg diffusion. A two-band model is used to solve for the electronic energy levels using parameters obtained from bulk data. Comparison with tentative experimental data implies that some effective shrinkage of the HgTe layers occurs. [ABSTRACT FROM AUTHOR]

It is known that the figure of merit ( ZT ) of thin nanowires can be significantly enhanced at room temperature due to the reduction of phonon thermal conductance arising from the increase of boundary scattering of phonons. It is expected that the phonon thermal conductance of nanowires filled with quantum dots (QDs) will be further reduced. Here we consider a superlattice nanowire (SLNW) modeled by a linear chain of strongly coupled QDs connected to electrodes. We study the dependence of ZT on the QD energy level ( E 0 ) (relative to the Fermi level E F in the electrodes), inter-dot coupling strength ( t c ), tunneling rate (Γ), and temperature T in order to optimize the design. It is found that at room temperature the maximum power factor occurs when ( E 0  −  E F )∕ k B T  ≈ 2.4 and Γ =  t c , a result almost independent of the number of QDs in SLNW as long as t c ∕ k B T  < 0.5. By using reasonable physical parameters we show that thin SLNW with cross-sectional width near 3 nm has a potential to achieve ZT  ≥ 3. [ABSTRACT FROM AUTHOR]