Analysis of the modified optical properties and band structure of GaAs12xSbx-capped InAs/GaAs quantum dots

Ulloa Herrero, José María and Llorens, J.M. and Moral, M. del and Bozkurt, M. and Koenraad, P.M. and Hierro Cano, Adrián (2012). Analysis of the modified optical properties and band structure of GaAs12xSbx-capped InAs/GaAs quantum dots. "Journal of Applied Physics", v. 112 (n. 7); pp.. ISSN 0021-8979. https://doi.org/10.1063/1.4755794.

Description

Title: Analysis of the modified optical properties and band structure of GaAs12xSbx-capped InAs/GaAs quantum dots
Author/s:
  • Ulloa Herrero, José María
  • Llorens, J.M.
  • Moral, M. del
  • Bozkurt, M.
  • Koenraad, P.M.
  • Hierro Cano, Adrián
Item Type: Article
Título de Revista/Publicación: Journal of Applied Physics
Date: October 2012
Volume: 112
Subjects:
Freetext Keywords: gallium arsenide, III-V semiconductors, indium compounds, k.p calculations, oscillator strengths, photoluminescence, quenching (thermal), scanning tunnelling microscopy, semiconductor quantum dots, thermal stability, valence bands
Faculty: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) (UPM)
Department: Otro
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Abstract

The origin of the modified optical properties of InAs/GaAs quantum dots (QD) capped with a thin GaAs1−xSbx layer is analyzed in terms of the band structure. To do so, the size, shape, and composition of the QDs and capping layer are determined through cross-sectional scanning tunnelling microscopy and used as input parameters in an 8 × 8 k·p model. As the Sb content is increased, there are two competing effects determining carrier confinement and the oscillator strength: the increased QD height and reduced strain on one side and the reduced QD-capping layer valence band offset on the other. Nevertheless, the observed evolution of the photoluminescence (PL) intensity with Sb cannot be explained in terms of the oscillator strength between ground states, which decreases dramatically for Sb > 16%, where the band alignment becomes type II with the hole wavefunction localized outside the QD in the capping layer. Contrary to this behaviour, the PL intensity in the type II QDs is similar (at 15 K) or even larger (at room temperature) than in the type I Sb-free reference QDs. This indicates that the PL efficiency is dominated by carrier dynamics, which is altered by the presence of the GaAsSb capping layer. In particular, the presence of Sb leads to an enhanced PL thermal stability. From the comparison between the activation energies for thermal quenching of the PL and the modelled band structure, the main carrier escape mechanisms are suggested. In standard GaAs-capped QDs, escape of both electrons and holes to the GaAs barrier is the main PL quenching mechanism. For small-moderate Sb (<16%) for which the type I band alignment is kept, electrons escape to the GaAs barrier and holes escape to the GaAsSb capping layer, where redistribution and retraping processes can take place. For Sb contents above 16% (type-II region), holes remain in the GaAsSb layer and the escape of electrons from the QD to the GaAs barrier is most likely the dominant PL quenching mechanism. This means that electrons and holes behave dynamically as uncorrelated pairs in both the type-I and type-II structures.

More information

Item ID: 16351
DC Identifier: http://oa.upm.es/16351/
OAI Identifier: oai:oa.upm.es:16351
DOI: 10.1063/1.4755794
Official URL: http://jap.aip.org/resource/1/japiau/v112/i7/p074311_s1?ver=pdfcov
Deposited by: Memoria Investigacion
Deposited on: 27 Jul 2013 10:22
Last Modified: 21 Apr 2016 16:39
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