The Interactions Between Misfit Dislocations in InGaAs/GaAs Interfaces
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THE INTERACTIONS INTERFACES.
BETWEEN MISFIT DISLOCATIONS IN InGaAs/GaAs
Philip Kightley, Peter J Goodhew and Richard Beanland. Department of Materials Science and Engineering, University of Liverpool, PO Box 147, Liverpool, England, L69 3BX. ABSTRACT. The reactions between misfit dislocations arriving by glide at the interface between an InO.12Gao.88As/GaAs multilayer and a GaAs substrate are analysed and reported. The glide forces for the (a/2) dislocations are calculated as a function of vicinal tilt from (001) to (100). It is observed that the 4% changes in the magnitude of the force for a 2' vicinal angle are not sufficient to significantly alter the relative linear densities of the different types of dislocation. INTRODUCTION. In this paper multilayers of InGaAs of =1% mismatch are studied by TEM. In the first section misfit dislocations present in the interface between the InGaAs and the GaAs substrate have been carefully analysed and the interfacial reactions catalogued. The analysis also allows the evaluation of the deformation tensor [1,2,3]. In this study vicinal substrates tilted from (001) to (100) have been used and the second section of this paper is concerned with the change in the (glide) force resolved onto the different dislocations because of the vicinal angle. This is calculated using the Hornstra-Bartels [4] model to determine the stress tensor which is substituted into the form of the Peach-Koehler formula suggested by Nabarro [5]. In previous publications it has been shown that growth on vicinal surfaces produces dislocations of intersecting line direction [6] and that polygonal dislocations centres can easily form [7] so these are not discussed in detail. OBSERVATIONS. 1
Array Interactions and the Total Deformation.
The reactions between the dislocations are grouped into approximately orthogonal and approximately parallel groups. Note that when growing on vicinal surfaces the intersections are not exactly orthogonal and dislocations also form low angle intersections. (i) OrthogonalReactionCentres. Figures la and b show (001) plan view TEM micrographs of the misfit dislocation array generated at the interface between a 10 period In0.l2Ga0.88 As/GaAs strained layer superlattice and its substrate. Only reactions that have occured at the approximately orthogonal intersection of the misfit dislocations are labelled. There are four reactions, A, B, C and D. Reaction A is between dislocations of like Burgers vector. Reaction B is a reaction between orthogonal dislocations which creates a sessile dislocation segment with its Burgers vector in the (001) plane. The C type reaction centres occur when an edge dislocation that is being formed by the glide out of the interface plane of existing glide dislocations crosses an orthogonal 600 dislocation. The centre D is a nonreaction (with a potential reaction of (aGaAsi 2 )[101] + (aGaAs/2)[10T] - (aGaAs)[100]). A type For a reaction of type A both sides of the intersection form dislocations with lines of approximately projection in approximately edge o
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