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Self-Diffusion as A Limiting Factor of a-SiGe Crystallization

Published online by Cambridge University Press:  15 February 2011

F. Edelman
Affiliation:
Faculty of Materials Engineering, Technion, 32000 Haifa, Israel, edelmann@tx.technion.ac.il
T. Raz
Affiliation:
Faculty of Materials Engineering, Technion, 32000 Haifa, Israel, edelmann@tx.technion.ac.il
Y. Komem
Affiliation:
Faculty of Materials Engineering, Technion, 32000 Haifa, Israel, edelmann@tx.technion.ac.il
P. Werner
Affiliation:
Max-Planck-Institute of Microstructure Physics, Weinberg 2.D-06120 Halle/Saale, Germany
W. Beyer
Affiliation:
Institute of Thin Film and Ion Technology, Research Centre, D-52425 Jiilich, Germany
R. Butz
Affiliation:
Institute of Thin Film and Ion Technology, Research Centre, D-52425 Jiilich, Germany
H. Zeindl
Affiliation:
Institute of Semiconductor Physics, Walter-Korsing-Straβe 2, 15230 Frankfurt (Oder), Germany.
P. Zaumseil
Affiliation:
Institute of Semiconductor Physics, Walter-Korsing-Straβe 2, 15230 Frankfurt (Oder), Germany.
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Abstract

Highly doped (∼1018 to 1021cm−3) polycrystalline Si1-xGex films, crystallized from amorphous (a) state at relative low temperatures, are prospective materials in a variety of applications, such as liquid-crystal displays, solar cells and integrated thermoelectric sensors on large-area glass substrates. Since the nature of the grains in the crystallized film defines properties such as carrier mobility, the nucleation and growth process of the a-SiGe films is of fundamental interest. We have studied the crystallization of undoped and highly doped (B or Ga) amorphous SiGe films. The films were deposited by RFCVD or molecular beam on oxidized (001)Si and for TEM study on cleaved NaCl. The incubation time and grain growth rate were studied by means of in situ TEM using a heating stage. The crystallization process in undoped SiGe followed Avrami relationship. An average grain size between 0.1 and 2μm was observed. However, the highly p-doped (with B or Ga) SiGe films crystallized to a stable nanocrystalline structure (grain size <10nm). The process of the a-SiGe crystallization is explained on the basis of self-diffusion. During the first stage, the nucleation of crystals is accompanied with nonequilibrium vacancy generation at the amorphous/crystalline interface. During the second stage, the growth of crystals takes place by vacancy outdiffusion which is hindered by B and Ga interaction with vacancies.

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Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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