406 research outputs found
Anisotropic and inhomogeneous Coulomb screening in the Thomas-Fermi approximation: Application to quantum dot-wetting layer system and Auger relaxation
International audienceA model for anisotropic and inhomogeneous Coulomb screening due to 2D and 3D carriers, is proposed in the Thomas–Fermi approximation. Analytical expressions for the screened interaction potentials and scattering matrix elements are obtained. This model is applied to the Auger relaxation of carriers in an InAs/InP quantum dot (QD) – wetting layer (WL) system. The influences of the QD morphology and carriers densities on screening and Auger effects are studied. 2D–2D scattering is found to be the most important process, depending especially on QD morphology. A smearing effect is associated to the wetting layer wavefunction extension along the growth axis. The screened potential is similar to a potential screened by 3D carriers
Semianalytical model for simulation of electronic properties of narrow-gap strained semiconductor quantum nanostructures
International audienceA complete semianalytical model is proposed for the simulation of the electronic, mechanical, and piezoelectric properties of narrow-gap strained semiconductor quantum nanostructures. A transverse isotropic approximation for the strain and an axial approximation for the strained 8x8 Hamiltonian are proposed. It is applied extensively to the case of InAs/InP quantum dots (QDs). Symmetry analysis shows that there does exist a nonvanishing splitting on the electron P states due to the coupling with valence band. This splitting, which was not considered before, is found to be smaller in InAs/GaAs QD than in InAs/InP QD. Analytic expressions for the first and second order piezoelectric polarizations are used to evaluate the perturbation of electronic states
Atomistic calculations of Ga(NAsP)/GaP(N) quantum wells on silicon substrate: Band structure and optical gain
International audienceBand structure calculations of strained Ga(NAsP) quantum wells are performed within the framework of the extended-basis sp3d5s* tight-binding model. The nitrogen contribution is taken into account by introducing an additional sN orbital into the tight-binding basis. Biaxial strain effects on the band alignment of bulk Ga(NAsP) is studied for the ultra-diluted regime. We demonstrate a good agreement with experimental data both for transition energies and optical gain in Ga(NAsP) quantum wells. The effect of N incorporation in the laser active areas is simulated
Impact of the capping layers on lateral confinement in InAs/InP quantum dots for 1.55 um laser applications srudied by magneto-photoluminescence.
We have used magnetophotoluminescence to study the impact of different capping layer material combinations (InP, GaInAsP quaternary alloy, or both InP and quaternary alloy) on lateral confinement in InAs/InP quantum dots (QDs) grown on (311)B orientated substrates. Exciton effective masses, Bohr radii, and binding energies are measured for these samples. Conclusions regarding the strength of the lateral confinement in the different samples are supported by photoluminescence at high excitation power. Contrary to theoretical predictions, InAs QDs in quaternary alloy are found to have better confinement properties than InAs/InP QDs. This is attributed to a lack of lateral intermixing with the quaternary alloy, which is present when InP is used to (partially) cap the dots. The implications of the results for reducing the temperature sensitivity of QD lasers are discussed. ©2005 American Institute of Physic
From k·p to atomic calculations applied to semiconductor heterostructures
International audienceWe present a brief overview of the main results obtained in our group for the simulation of electronic and optical properties of semiconductor heterostructures. A short introduction is given on InAs quantum dots, grown on InP, GaAs and GaP substrates. It is shown that 1-band k·p calculations can be used in the reciprocal space, in order to get a simulation of perfectly ordered array of quantum dots. A semianalytical modeling is also presented, including an axial approximation of the 8*8 band k·p calculations. Linear and nonlinear contributions to piezoelectricity are discussed. A complete 8*8 band k·p approach is then used to show the properties of InAs/InP quantum dots, with different substrate orientations. Finally, a study of the highly strained InAs/GaP interface is performed with a first principle modeling using ABINIT packages. Band lineups and evolution of gap energies are calculated, and compared to those found by Chuang et al. [1
Electronic wave functions and optical transitions in (In,Ga)As/GaP quantum dots
Robert, CĂ©dric et al.We study the complex electronic band structure of low In content InGaAs/GaP quantum dots. A supercell
extended-basis tight-binding model is used to simulate the electronic and the optical properties of a pure
GaAs/GaP quantum dot modeled at the atomic level. Transitions between hole states confined into the dots
and several XZ-like electronic states confined by the strain field in the GaP barrier are found to play the main
role on the optical properties. Especially, the calculated radiative lifetime for such indirect transitions is in
good agreement with the photoluminescence decay time measured in time-resolved photoluminescence in the
µs range. Photoluminescence experiments under hydrostatic pressure are also presented. The redshift of the
photoluminescence spectrum with pressure is also in good agreement with the nature of the electronic confined
states simulated with the tight-binding model.A.R.G. and M.I.A. acknowledge support from the Spanish
Ministry of Economy and Competitiveness (MINECO)
through Grant No. MAT2009-09480 (PIEZOHM) and Severo
Ochoa Excellence Centre Award (No. SEV-2015-0496).
M.O.N. acknowledges financial support from the Russian
Foundation for Basic Research. This research is supported by
“Region Bretagne” through the PONANT project including ´
FEDER funds. This paper is also supported by the OPTOSI
Agence Nationale pour la Recherche Project No. 12-BS03-
002-02. This work has been performed using HPC resources of
GENCI CINES, TGCC/CCRT, and IDRIS under the allocation
No. 2013-[x2013096724].Peer reviewe
Theoretical study of optical properties of anti phase domains in GaP
International audienceIII-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic "coherent" growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter, we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface
Multijunction photovoltaics: integrating III–V semiconductor heterostructures on silicon
International audienceGallium arsenide phosphide nitride shows promise for developing highefficiency tandem solar cells on low-cost silicon substrate
Réalisation d’un laser à faible courant de seuil, avec des boites quantiques InAs/InP organisées et couplées latéralement
Nous présentons ici la réalisation d’un laser à faible courant de seuil avec des boites quantiques (QDs) organisées et couplées InAs/InP sur subsstrat (311)B pour une émission à 1.55 m. En effet, pour des hautes densités de QDs, une organisation périodique apparaît dans le plan. Cette organisation renforce le couplage latéral inter-boites. Des expériences de magnéto-photoluminescence permettent de mettre en évidence ces effets de couplage. Ce couplage améliore l’injection des porteurs. Une émission laser avec des faibles courants de seuil est obtenue avec de telles boites
Theoretical study of highly strained InAs material from first-principles modelling: application to an ideal QD
International audienceWe study the properties of highly strained InAs material calculated from first principles modeling using ABINIT packages. We first simulate the characteristic of bulk InAs crystal and compare them with both experimental and density functional theory (DFT) results. Secondly, we focus our attention on the strain effects on InAs crystal with a gradual strain reaching progressively the lattice matched parameters of InP, GaAs and GaP substrates. The final part is dedicated to the study of a hypothetic spherical InAs/GaP quantum dot. The effect of hydrostatic deformations for both InAs Zinc-Blende phase and InAs RockSalt phase is discussed
- …