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Ge Island evolution during growth, in-situ anneal, and Si capping in an industrial CVD reactor Roger Loo*, Philippe Meunier-Beillard*1, Didier Dentel**2, Michael Goryll**, Danielle Vanhaeren*, Lili Vescan**, Hugo Bender*, Matty Caymax*, Wilfried Vandervorst* * IMEC, Kapeldreef 75, B-3001 Leuven, ** Institute of Thin Films and Ion Technology, Research Centre Jülich, D-52425 Jülich 1 Present address: Philips Research Leuven, Kapeldreef 75, B-3001 Leuven 2 Present address: Laboratoire de Physique et de Spectroscopie Electronique UPRES-A CNRS 7014, Universite de Haute Alsace, 4, rue des Freres Lumiere, F-68093 Mulhouse Cedex

ABSTRACT Si based nanostructures such as Ge or Si1-xGex dots embedded in Si receive a lot of attention. This interest is driven by the reduction of device sizes as well as by their possible use in optoelectronic applications, as a possible solution to improve the radiative light emission. In this paper we give a detailed overview of the growth kinetics as observed for Ge growth in a standard production oriented chemical vapor deposition system. The island morphology and density are controlled by varying the growth conditions or by applying a thermal anneal after the island growth. Island densities up to 2.3x1010 cm-2 have been obtained for depositions at 650°C. With increasing deposition time, the usual change-over from monomodal to bimodal island distribution is pointed out and this change-over depends on the critical island diameter, which decreases with decreasing growth temperature. Applying a thermal budget after the island growth initiates Ge surface diffusion and Si diffusion from the substrate through the islands. This results in an enhancement of the island diameter and height, and also in a reduction of island density. Furthermore, depending on the island distribution after Ge deposition, a transition from pyramid to dome or visa versa is observed after the in-situ anneal. Optical device structures require a Si cap layer. However, Si capping at 700°C, leads to a nearly total dissolution of small islands and a truncation of bigger dome-shaped islands. This can be prevented by reducing the deposition temperature and by changing the Si gas source. Clear island luminescence, is observed up to 200K and lies in the spectral range of 1.35-1.50µm, which is interesting from the point of view of applications. In particular, this shows the potential of this material system for opto-electronic device applications. In spite of the fact that the observed PL intensity is comparable to the best reported values, we could further enhance it by a thermal treatment in a H2 plasma.

INTRODUCTION The interest of Si based nanostructures is due to their compatibility with conventional Si integrated-circuit technology. Self-organizing island growth (Stranski-Krastanov growth) of SiGe or Ge on Si may be used to fabricate quantum size dots with high densities, without the need of lithography to prepare small structures. In general, Stranski-Krastanov growth appears only above a critical Ge content, which strongly d