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Formation of InAs quantum dots and wetting layers in GaAs and AlAs analyzed by cross-sectional scanning tunneling microscopy |
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| Authors: | P Offermans PM Koenraad JH Wolter K Pierz M Roy PA Maksym |
| Institution: | aDepartment of Semiconductor Physics, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands;bPhysikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany;cDepartment of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK |
| Abstract: | We have used cross-sectional scanning-tunneling microscopy (X-STM) to compare the formation of self-assembled InAs quantum dots (QDs) and wetting layers on AlAs (1 0 0) and GaAs (1 0 0) surfaces. On AlAs we find a larger QD density and smaller QD size than for QDs grown on GaAs under the same growth conditions (500 °C substrate temperature and 1.9 ML indium deposition). The QDs grown on GaAs show both a normal and a lateral gradient in the indium distribution whereas the QDs grown on AlAs show only a normal gradient. The wetting layers on GaAs and AlAs do not show significant differences in their composition profiles. We suggest that the segregation of the wetting layer is mainly strain-driven, whereas the formation of the QDs is also determined by growth kinetics. We have determined the indium composition of the QDs by fitting it to the measured outward relaxation and lattice constant profile of the cleaved surface using a three-dimensional finite element calculation based on elasticity theory. |
| Keywords: | X-STM Semiconducting III– V materials Relaxation Strain Molecular beam epitaxy Quantum dots |
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