C. Girardeaux, et al.
J. Phys. IV France 132 (2006) 163-170
Effect of thermal annealing on the optical properties of self-assembled Ge/Si quantum dotsT.K. Nguyen-Duc1, V. Le Thanh1, 0, J. Derrien1, V. Yam2, P. Boucaud2 and D. Bouchier2
1 Centre de Recherche en Matière Condensée et Nanosciences (CRMC-N CNRS), Laboratoire associé à l'Université de la Méditerranée (Aix-Marseille II) et l'Université Paul Cézanne (Aix-Marseille III), Campus de Luminy, Case 913, 13228 Marseille Cedex 9, France
2 Institut d'Électronique Fondamentale, UMR-CNRS 8622, Université Paris-Sud, 91405 Orsay Cedex, France
The kinetic formation of self-assembled Ge/Si hut clusters grown by ultra-high vacuum chemical-vapour deposition has been investigated by means of reflection high-energy electron diffraction, atomic force microscopy and photoluminescence spectroscopy. We show that point defects that are induced in the epilayers grown at substrate temperatures below 525 °C greatly influence the optical properties of Ge/Si hut clusters. We have investigated two approaches of sample annealing in order to remove point defects while minimizing Ge/Si intermixing: a long annealing at the growth temperature and a rapid annealing up to a temperature of 900 °C for a very short period of time. The obtained results appear to indicate that the long annealing at the growth temperature allows reducing the contribution of point defects, giving rise to the observation of the proper photoluminescence of the Ge/Si hut clusters. However, the long annealing could not completely remove point defects. A well-controlled rapid thermal annealing for a very short period of time is shown, on the other hand, to be efficient for removing point defects and minimize the Ge/Si intermixing. Our experiments illustrate a correlation between the increase of Ge/Si intermixing and the evolution of the optical properties from a quantum-dot to a quantum-well behaviour.
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