Atomic processes in molecular beam epitaxy on strained InAs(137): A density-functional theory study

The atomic processes in molecular beam epitaxy of InAs on the InAs(137) surface are investigated by means of first-principles total-energy calculations. We consider layer-by-layer growth on InAs(137) facets as a typical process during the evolution of shallow InAs islands in the Stranski-Krastanov growth mode of InAs on GaAs that is exploited for the self-assembly of heteroepitaxial quantum dots. From the calculated energetics we conclude that a growth scenario where an As2 molecule adsorbs on a single In adatom, followed by capture of another In adatom, is most likely. Moreover, our calculations of the potential-energy surface for In adatoms on the InAs(137) surface show that In adatoms are highly mobile. Surface diffusion on InAs(137) is found to be almost isotropic with energy barriers 2 molecule is destabilized by compressive strain in excess of −5%. This finding leads us to the conclusion that layer growth on InAs(137) facets ceases in highly strained regions of InAs islands on GaAs, in line with the observed shape evolution of such islands

Erratum: Analytic many-body potential for InAsÕGaAs surfaces and nanostructures: Formation energy of InAs quantum dots [Phys. Rev. B 77, 235303 (2008)]

In our paper we have proposed a parametrization of the Abell-Tersoff potential for In, Ga, As, InAs and GaAs. This is to report corrections to the results presented there. Specifically, surface energies of non-stoichiometric surfaces, quoted for a specific value of the arsenic chemical potential, were in error due to inconsistent usage of the As chemical potential. The correct surface energies as calculated with the previously published parametrization T1,1 T2,2 T3,3 T4,4 T5,5 T6,6 T7,7 and our parametrization (denoted as T9) are reported in Tables I and II, replacing the according entries in Tables VII to X of our paper. The surface energies of stoichiometric surface reconstructions and the relaxation differences (||F0|| and ‹Δr›) given in these original Tables are not shown here as they are not affected by the inconsistent usage of the As chemical potential. The correct surface energies of our parametrization (T9) deviate from the DFT values since the inconsistent usage of the As chemical potential obstructed the fitting of parameters. In extension to Sec. III.C and Sec. III.D of our paper, we note that the relaxation of surface slabs was limited to 100 iterations and that T5 referred to a modified version of the parameters from Ref. 5 using Rcij=3.1 Å and Dcij=0.1 Å as cutoff parameters for the As-As interaction. These cutoff parameters effectively define a nearest-neighbour scheme in order to reproduce the results for the GaAs bulk phases presented in the original work.5 For potential parameters T8,8 we again report all surface energies. Previous results were ambiguous, because the cutoff parameters for the potential T8 had not been provided in Ref. 8. The new results reported in Table IV and V are obtained with the cutoff parameters listed in Table III

Analytic many-body potential for InAs/GaAs surfaces and nanostructures: Formation energy of InAs quantum dots

A parametrization of the Abell–Tersoff potential for In, Ga, As, InAs, and GaAs is presented by using both experimental data and results from density-functional calculations as input. This parametrization is optimized for the description of structural and elastic properties of bulk In, Ga, As, InAs, and GaAs, as well as for the structure and energy of several reconstructed low-index GaAs and InAs surfaces. We demonstrate the transferability to GaAs and InAs high-index surfaces and compare the results to those obtained with previously published parametrizations. Furthermore, we demonstrate the applicability to epitaxial InAs/GaAs films by comparing the Poisson ratio and elastic energy for biaxial strain, as obtained numerically with our potential and analytically from continuum-elasticity theory. Limitations for the description of point defects and surface diffusion are pointed out. This parametrization enables us to perform atomically detailed studies of InAs/GaAs heterostructures. The formation energy of InAs quantum dots on GaAs(001) obtained from our atomistic approach is in good agreement with previous results from a hybrid approach

Control of fine-structure splitting and excitonic binding energies in selected individual InAs/GaAs quantum dots

A systematic study of the impact of annealing on the electronic properties of single InAs/GaAs quantum dots (QDs) is presented. Single QD cathodoluminescence spectra are recorded to trace the evolution of one and the same QD over several steps of annealing. A substantial reduction of the excitonic fine-structure splitting upon annealing is observed. In addition, the binding energies of different excitonic complexes change dramatically. The results are compared to model calculations within eight-band k.p theory and the configuration interaction method, suggesting a change of electron and hole wave function shape and relative position.Comment: 4 pages, 4 figure

Analytic many-body potential for GaAs(001) homoepitaxy: Bulk and surface properties

We employ atomic-scale simulation methods to investigate bulk and surface properties of an analytic Tersoff- Abell type potential for describing interatomic interactions in GaAs. The potential is a modified form of that proposed by Albe and colleagues [Phys. Rev. B 66, 035205 (2002)] in which the cut-off parameters for the As-As interaction have been shortened.With this modification, many bulk properties predicted by the potential for solid GaAs are the same as those in the original potential, but properties of the GaAs(001) surface better match results from first-principles calculations with density-functional theory (DFT). We tested the ability of the potential to reproduce the phonon dispersion and heat capacity of bulk solid GaAs by comparing it to experiment and the overall agreement is good. In the modified potential, the GaAs(001) β2(2 × 4) reconstruction is favored under As-rich growth conditions in agreement with DFT calculations. Additionally, the binding energies and diffusion barriers for a Ga adatom on the β2(2 × 4) reconstruction generally match results from DFT calculations. These studies indicate that the potential is suitable for investigating aspects of GaAs(001) homoepitaxy

Increased fluorescence of PbS quantum dots in photonic crystals by excitation enhancement

We report on the enhanced fluorescence of lead sulfide quantum dots interacting with leaky modes of slab type silicon photonic crystals. The photonic crystal slabs were fabricated, supporting leaky modes in the near infrared wavelength range. Lead sulfite quantum dots which are resonant in the same spectral range were prepared in a thin layer above the slab. We selectively excited the leaky modes by tuning the wavelength and angle of incidence of the laser source and measured distinct resonances of enhanced fluorescence. By an appropriate experiment design, we ruled out directional light extraction effects and determined the impact of enhanced excitation. Three dimensional numerical simulations consistently explain the experimental findings by strong near field enhancements in the vicinity of the photonic crystal surface. Our study provides a basis for systematic tailoring of photonic crystals used in biological applications such as biosensing and single molecule detection, as well as quantum dot solar cells and spectral conversion application