Vacancy-mediated intermixing in InAs/InP(001) quantum dots subjected to ion implantation
- Regroupement Quebecois sur les Materiaux de Pointe (RQMP), Departement de Genie Physique, Ecole Polytechnique de Montreal, Montreal, Quebec H3C 3A7 (Canada)
- Regroupement Quebecois sur les Materiaux de Pointe (RQMP), Departement de Physique, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada)
- Department of Physics, Acadia University, Wolfville, Nova Scotia B4P 2R6 (Canada)
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5 (Canada)
- Institute for Microstructural Sciences, National Research Council, Ottawa, Ontario K1A 0R6 (Canada)
We have investigated the influence of defects emanating from phosphorus implantation damage in the InP capping layer on postgrowth thermally induced intermixing in self-assembled InAs/InP(001) quantum dots (QDs). Photoluminescence (PL) spectra from as-grown samples could be described as the superposition of separate PL peaks where each peak corresponded to emission from an ensemble of QDs with a particular height ranging from 4 to 13 ML. Blueshift of up to 270 meV and significant bandwidth broadening were observed in the PL spectra after ion implantation with a fluence of 5x10{sup 11}-10{sup 14} cm{sup -2} and subsequent annealing at temperatures ranging from 450 to 600 deg. C. From the analysis of the evolution of the QD peaks upon intermixing, which revealed the coexistence of intact QD PL and a broad PL feature related to heavily intermixed QDs, it was suggested that the bandwidth broadening resulted from spatial inhomogeneity in the compositional intermixing. In order to better understand the mechanism responsible for the ion-implantation-induced intermixing, samples capped with a stack of compressively strained In{sub 0.75}Ga{sub 0.25}As/InP quantum wells (QWs) were prepared to trap vacancies released by the implantation damage while not inhibiting the effect of the interstitials. Both blueshift and bandwidth broadening were suppressed in samples containing the strained InGaAs QWs, whereas the evolution of the PL spectra from the QDs behaves as expected for interstitial-mediated intermixing. The vacancies were thus believed to be trapped in the QWs and indicated that intermixing in ion-implanted InP capped samples is mediated by vacancies. The shape of the QDs changed from a truncated pyramid in the as-grown state to a double convex lens structure after intermixing as confirmed by cross-sectional scanning transmission electron microscopy imaging. Furthermore, the change in shape and compositional intermixing of the QDs were attributed to vacancy trapping in the vicinity of the QDs as based on atomistic strain calculations.
- OSTI ID:
- 21137449
- Journal Information:
- Journal of Applied Physics, Vol. 104, Issue 4; Other Information: DOI: 10.1063/1.2970093; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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