The effect of misorientation of the GaAs substrate on the properties of InAs quantum dots grown by low-temperature molec
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The Effect of Misorientation of the GaAs Substrate on the Properties of InAs Quantum Dots Grown by Low-Temperature Molecular Beam Epitaxy A. A. Tonkikha, c^, G. E. Cirlina, c, N. K. Polyakova, Yu. B. Samsonenkoa, b, V. M. Ustinovb, N. D. Zakharovc, P. Wernerc, V. G. Talalaevc, d, and B. V. Novikovd aInstitute
for Analytical Instrumentation, Russian Academy of Sciences, Rizhskiœ pr. 26, St. Petersburg, 190103 Russia ^e-mail: [email protected] bSt. Petersburg Physicotechnical Scientific and Educational Center, Russian Academy of Science, St. Petersburg, 195220 Russia cMax-Planck Institute of Microstructure Physics, 06120 Halle (Saale), Germany dFok Institute of Physics, St. Petersburg State University, Ulyanovskaya 1, St. Petersburg–Petrodvorets, 198504 Russia Submitted October 5, 2005; accepted for publication October 17, 2005
Abstract—The structural and optical properties of arrays of InAs quantum dots grown on GaAs substrates at relatively low temperatures (250 and 350°C) and with various degrees of misorientation of the surface are studied. It is shown that low-temperature growth is accompanied by the formation of quantum dot clusters along the dislocation loops on the singular surface and along the steps caused by the surface vicinality on the misoriented surface. The formation of quantum dot clusters leads to the appearance of a new long-wavelength band in the exciton photoluminescence (PL) spectra. It is found that the degrees of polarization of the PL spectral band for clusters of various shapes are different. PACS numbers: 68.65.Hb, 78.67.Hc, 73.63.Kv, 78.55.Cr DOI: 10.1134/S1063782606050137
1. INTRODUCTION Numerous studies are devoted to examination of the properties and mechanisms of formation of semiconductor quantum dots (QDs) in the context of searching for possible applications of these dots in new optoelectronic devices [1, 2]. The InAs islands on the GaAs surface are formed during molecular beam epitaxial (MBE) growth in the Stranskii–Krastanov mode. In this case, the typical growth temperatures are 450–500°C. In this temperature range, the In atoms are desorbed from the substrate surface only slightly, and the epitaxial layers are sufficiently high-quality from the viewpoint of their device applications. According to the theoretical calculations [3], as the growth temperature decreases, the QDs decrease in size while their density increases, which was observed experimentally [4, 5]. However, the range of lower temperatures 250–350°C still remains poorly studied. In this context, the issue concerning the behavior of the QD array at these growth temperatures emerges. In this study, this issue is studied in detail by methods of transmission electron microscopy (TEM) and photoluminescence (PL).
2. EXPERIMENTAL The structures under study were grown on GaAs semi-insulating substrates by MBE using an ÉP1203 installation. The InAs layer was grown on a GaAs buffer layer at the deposition temperatures 250 or 350°C. Then the InAs layer was overgrown with a thin (5 nm) GaAs layer at the
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