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Dislocation Behaviour in GexSi1-x Epilayers on (001)Si

Published online by Cambridge University Press:  28 February 2011

Eric P. Kvam ,
D.M. Maher  and
C.J. Humphreys
Eric P. Kvam
Affiliation:
Department of Materials Science and Engineering, The University, Liverpool L69 3BX Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, 1 Cyclotron Road, Berkeley, CA 94720
D.M. Maher
Affiliation:
Department of Materials Science and Engineering, The University, Liverpool L69 3BX AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill, NJ 07974
C.J. Humphreys
Affiliation:
Department of Materials Science and Engineering, The University, Liverpool L69 3BX
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Abstract

We have observed that the nature of misfit dislocations introduced near the critical thickness in GexSi1-x alloys on (001)Si changes markedly in the region 0.4 ≤ x ≤ 0.5. At or below the lower end of this compositional range, the observed microstructure is comprised almost entirely of 60° type dislocations, while at the high end, the dislocation structure is almost entirely Lomer edge type. Concurrent with this change, the dislocation density at the top of the epilayer varies by a factor of about 60X. Similarly, several other observables (e.g. dislocation length and spacing) also change appreciably.

Part of the reason for the morphological variation seems to be a change in the source for dislocation introduction, in conjunction with a change in glide behaviour of dislocations as a function of film thickness. Evidence will be presented that indicates strain, as well as thickness, has a critical value for some dislocation introduction mechanisms, and that these together determine the resulting microstructure.

Furthermore, it appears unlikely that the edge-type Lomer dislocations which appear at about x = 0.5 are either introduced directly, by climb, or grown in, as in the three-dimensional island growth and coalescence which occurs when x approaches unity. Instead, a two-step mechanism involving glissile dislocations is proposed and discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 160 , 1989 , 71
Copyright
Copyright © Materials Research Society 1990

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