New Approach to Growth of High-Quality GaAs Layers on Si Substrates

Varrio, J.; Salokatve, A.; Asonen, H.; Hovinen, M.; Pessa, M.; Ishida, Kenji; Kitajima, Hiroshi

doi:10.1557/proc-116-91

Cited by 8 publications

(3 citation statements)

References 11 publications

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“…The rotation of the (001) plane of the layer is found to be in the opposite direction to that given by the simple tilt model or the Poisson effect (e.g. Schowalter 1988, Varrio 1988, Stolz 1988). If there is no relief of the tensile strain developed in the film, there should be a rotation of -15" for an offcut of 4%.…”

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confidence: 59%

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Tilts in Thin Strained Layers.

Beanland

1991

MRS Proc.

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There is considerable interest at present in the mechanisms of tilting of epitaxial films, such that low index planes in layer and substrate have slightly different orientations. There are two primary causes of this effect: a) coherency strains and b) the action of misfit dislocations. It is important to distinguish between the two effects, particularly in the case of strained layers used for band-gap engineering. Using a recent formulation of the Frank-Bilby equation for the dislocation content of interfaces, it is shown how planes may be rotated in coherent layers due to both the Poisson effect and anisotropic misfit. An advantage of the Frank-Bilby equation is that it allows consideration of semicoherent layers. It is shown that a side effect of misfit dislocation introduction can be to introduce a further rotation of the epitaxial layer. Both these effects have been measured experimentally. The amount and the sense of rotation is compared to theory.The rotation of planes in epitaxial layers is at present a matter of some interest and poorly understood. It has been noted in every lattice mismatched system , and has been proposed as an important mechanism of misfit relief, particularly in strained layers grown on offcut substrates. Here an analysis of the sources of rotation is presented and compared to experimental measurements.The state of strain in a layer which is constrained to fit the substrate can be described in terms of continuum elasticity or a dislocation model. Both approaches give the same results (Beanland 1991). The deformation of an elastically isotropic layer subject to a biaxial strain can be described by the matrix D, with the components D 11 =f, D 22 =f, D 33 =-2fv/(l-v), D 1 2 =D 1 3 =D 2 3 =D 32 =D 3 1 =D 21 =0(1)where f is the misfit strain, i.e. (ae-as)/ae and v is Poisson's ratio; D is written in an orthogonal reference frame Q2, with x0 and yn in the interface plane and za pointng from the interface to the layer surface. This describes a tetragonal distortion of the layer, as shown in figure 1. When the layer is strained to fit the substrate, the dimensions parallel to the interface contract, and the dimension perpendicular to the interface expands due to the Poisson effect. It can be seen that only planes parallel and perpendicular to the interface do not have their orientation changed by the distortion. In the unstrained layer (figure la) planes in the layer m are parallel to similar planes m' in the substrate. When the layer is strained (figure lb), the plane (m") is no longer parallel to m'. It can be shown that, in elastically isotropic layers, a plane at an angle 0 to the interface will be rotated by an angle AO given by tanA0 +v) f sine cosOIn the case of growth on substrates offcut from a low index surface, the low index planes in layer and substrate are no longer parallel due to this effect (figure 2). Figure 3 plots AO as a function of offcut angle for coherently strained Ino. 4 73 Gao. 527 As layers on InP. The curve of Mat.

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confidence: 59%

“…This rotation must therefore arise from the action of 60* dislocations. An interesting point was raised by Varrio et al (1988), who noted that different growth methods could lead to vastly different rotations. It was found that the rotation was much less when a pulsed beam was used in MBE rather than the usual continuous beam.…”

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confidence: 99%

Tilts in Thin Strained Layers.

Beanland

1991

MRS Proc.

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“…The question of the origin of the misorientation in epitaxially grown heterostructures is presently a matter of controversy. For instance, for a Si substrate, Varrio et al [20] noted that different GaAs growth methods can lead to vastly different rigid-body misorientations. The preparation of the substrate surface is consequently an important parameter (miscut angle, ªepireadyº or previously chemically treated surface), as well as the deposition parameters (temperature, species fluxesF F F).…”

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confidence: 99%

Electron Microscopy of Nanoledges at the (001)InAs/(001)GaAs Interface for an Approximate Orientation Relationship

Youssef

Fnaiech

Chen

et al. 1999

phys. stat. sol. (a)

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The structure of the InAs/GaAs(001) epitaxial heterointerface is observed by high resolution electron microscopy (HREM) along [110] when there is a slight long range angular misorientation between the two crystals around the common observation direction. The lattice misfit and the local misorientation (η = 6.9%, Δθ = 1.5°) are simultaneously accommodated via a non planar and non pseudoperiodic distribution of defects involving usual 90° and 60° dislocation cores and yet unreported nanoledges with exotic Burgers vector contents. One of these nanoledges is five (001) planes high and has a total Burgers vector content equal to (1/6)[33‐1]. Its local elastic field has been analysed in terms of ribbon‐like Somigliana dislocations. It depends on η, Δθ and its nanoledge height. Comparisons between the experimental and calculated tunnel positions between atom columns are given to appreciate the validity of the model.

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