A. J. Williamson

Comparison of two methods for describing the strain profiles in quantum dots

The electronic structure of interfaces between lattice-mismatched semiconductors is sensitive to the strain. We compare two approaches for calculating such inhomogeneous strain—continuum elasticity [(CE), treated as a finite difference problem] and atomistic elasticity. While for small strain the two methods must agree, for the large strains that exist between lattice-mismatched III-V semiconductors (e.g., 7% for InAs/GaAs outside the linearity regime of CE) there are discrepancies. We compare the strain profile obtained by both approaches (including the approximation of the correct C2 symmetry by the C4 symmetry in the CE method) when applied to C2-symmetric InAs pyramidal dots capped by GaAs.

Comparison of the k⋅p and direct diagonalization approaches to the electronic structure of InAs/GaAs quantum dots

We present a comparison of the 8-band k⋅p and empirical pseudopotential approaches to describing the electronic structure of pyramidal InAs/GaAs self-assembled quantum dots. We find a generally good agreement between the two methods. The most significant differences found in the k⋅p calculation are (i) a reduced splitting of the electron p states (3 vs 24 meV), (ii) an incorrect in-plane polarization ratio for electron-hole dipole transitions (0.97 vs 1.24), and (iii) an over confinement of both electron (48 meV) and hole states (52 meV), resulting in a band gap error of 100 meV. We introduce a “linear combination of bulk bands” technique which produces results similar to a full direct diagonalization pseudopotential calculation, at a cost similar to the k⋅p method.

Pseudopotential study of electron-hole excitations in colloidal free-standing InAs quantum dots

Excitonic spectra are calculated for free-standing, surface passivated InAs quantum dots using atomic pseudopotentials for the single-particle states and screened Coulomb interactions for the two-body terms. We present an analysis of the single particle states involved in each excitation in terms of their angular momenta and Bloch-wave parentage. We find that (i) in agreement with other pseudopotential studies of CdSe and InP quantum dots, but in contrast to k.p calculations, dot states wavefunction exhibit strong odd-even angular momentum envelope function mixing (e.g.

Prediction of a strain-induced conduction-band minimum in embedded quantum dots

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Multi-excitons in self-assembled InAs/GaAs quantum dots: A pseudopotential, many-body approach

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Theoretical interpretation of the experimental electronic structure of lens-shaped self-assembled InAs/GaAs quantum dots

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InAs quantum dots: Predicted electronic structure of free-standing versus GaAs-embedded structures

) and large valence-conduction coupling. (ii) While the pseudopotential approach produced very good agreement with experiment for free-standing, colloidal CdSe and InP dots, and for self-assembled (GaAs-embedded) InAs dots, here the predicted spectrum does {\em not} agree well with the measured (ensemble average over dot sizes) spectra. (1) Our calculated excitonic gap is larger than the PL measure one, and (2) while the spacing between the lowest excitons is reproduced, the spacings between higher excitons is not fit well. Discrepancy (1) could result from surface states emission. As for (2), agreement is improved when account is taken of the finite size distribution in the experimental data. (iii) We find that the single particle gap scales as

Parallel Empirical Pseudopotential Electronic Structure Calculations for Million Atom Systems

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Optical spectroscopy of single quantum dots at tunable positive, neutral, and negative charge states

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Electronic structure consequences of In/Ga composition variations in self-assembled In{sub x}Ga{sub 1-x}As/GaAs alloy quantum dots

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