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Influence Of Substrate Off-Cut On The Defect Structure In Relaxed Graded Si-Ge/Si Layers

Published online by Cambridge University Press:  15 February 2011

Srikanth B. Samavedam ,
F. Romanato ,
M. S. Goorsky  and
E. A. Fitzgerald
Srikanth B. Samavedam
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
F. Romanato
Affiliation:
INFM-Department of Physics “G. Galilei”, University of Padova, via Marzolo 8, Padova, Italy
M. S. Goorsky
Affiliation:
Department of Materials Science and Engineering, University of California, Los Angeles, CA 90095
E. A. Fitzgerald
Affiliation:
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139
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Abstract

Relaxed graded Si-Ge/Si layers can be used in a variety of micro-electronics applications such as templates for III-V/Si integration, in high speed field effect transistor (FET) structures and as detectors in optical communication. Each of these applications requires a different final Ge concentration in the graded Si-Ge layer. With increasing Ge content in the graded layer, some of the materials concerns that need to be addressed are- (i) a high surface roughness, (ii) the formation of dislocation pile-ups, and (iii) an increase in the threading dislocation density. We have shown that there is a substantial improvement in the surface roughness and the dislocation pile-up density of the graded Si-Ge layers by depositing on (001) 6° off-cut substrates. The substrate miscut also facilitates favorable intersections of {111} planes that aid reactions between the 60° dislocations to form edge dislocations with Burgers vectors of the type 1/2<110> and <100> resulting in a novel hexagonal dislocation structure. Such reactions occurred more readily in the Ge-rich regions of the graded layers where the growth temperature was high enough to aid dislocation climb. The edge dislocations with in-plane Burgers vectors lack a tilt component and the decreased rate of tilting in the Ge-rich regions is confirmed by triple crystal X-ray reciprocal space maps. This novel dislocation structure offers opportunities to explore new processes which may eliminate spatially variant strain fields in relaxed epitaxial layers.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 442: Symposium E – Defects in Electronic Materials II , 1996 , 343
Copyright
Copyright © Materials Research Society 1997

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