We investigate the microstructure of polycrystalline silicon films (grain size, texture and grain boundary population) on glass substrates. These films are produced from amorphous silicon precursor layers by scanning the raw beam of a continuous wave Ar+- ion laser operated at a wavelength of 514 nm over the amorphous silicon thereby crystallizing it. The materials applicability for devices in large area electronics strongly depends on the orientation of the surface normal, the average grain size and the defect density and population. Transmission electron microscopy together with electron back-scattering diffraction analysis of the crystallized layers reveal grain widths of about 10μm and grain lengths of several 10 μm. Under certain procesing conditions a preferred (001)-surface normal orientation (texture) forms. The grain boundary population is dominated in the textured films by coincidence boundaries, essentially twin boundaries of first and second order as well as Σ=5 boundaries.

Using liquid phase epitaxy from Bi solution in the temperature range 550°–700°C at low growth rates we study the formation of ripples and islands and their interdependence. As main results we find from the dependencies on growth time and temperature that ripples are an instability phenomenon and that islands nucleate thermally activated. Island nucleation on a ripple template (that is, as an instability phenomenon, highly ordered) has huge impact on the achievable order of the islands.

Various methods have been used to initiate growth by Molecular Beam Epitaxy (MBE) of GaN on sapphire, or other substrates, but there is always a problem with morphology and with a high defect density which results in the formation of a sub-grain boundary structure. We show that by using, homo-epitaxial growth on properly prepared bulk GaN substrates, combined with high temperature growth, we obtain a significant improvement in surface morphology. Growth at sufficiently high temperature leads to a rapid smoothing of the surface and to almost atomically flat surfaces over relatively large areas. Multi-Quantum Well structures grown on such GaN epitaxial films are dislocation free with abrupt interfaces.

We have optimized the sensitivity of convergent beam electron diffraction (CBED) by orienting the specimen such that the central (000) diffraction disc shows a pattern of defect lines that are most sensitive to tetragonal distortion. We compare the position of these lines in the experimentally obtained patterns with results from computer simulations, which need to be based on dynamical diffraction theory. In both experimental and simulated patterns the positions of the defect lines are determined by applying a Hough transformation. As a result of this optimized approach, we can measure the tetragonal distortion of a low temperature grown GaAs layer as low as 0.04%.

Various methods have been used to initiate growth by Molecular Beam Epitaxy (MBE) of GaN on sapphire, or other substrates, but there is always a problem with morphology and with a high defect density which results in the formation of a sub-grain boundary structure. We show that by using, homo-epitaxial growth on properly prepared bulk GaN substrates, combined with high temperature growth, we obtain a significant improvement in surface morphology. Growth at sufficiently high temperature leads to a rapid smoothing of the surface and to almost atomically flat surfaces over relatively large areas. Multi-Quantum Well structures grown on such GaN epitaxial films are dislocation free with abrupt interfaces.

Risers and treads on terraced surfaces of modified-Lely (M-Lely) grown 6H-SiC(0001) bulk crystals are investigated by reflection electron microscopy (REM). On risers we find parallel steps, with a height of one or two unit cells. On treads we find in addition to growth spirals island formation. We take these observations to conclude that two competitive processes operate in parallel, the step-flow mode and the two-dimensional nucleation.

Using finite elements we quantitatively calculate the inhomogeneous strain distribution associated with the so called crosshatch pattern. This pattern is a twodimensional, pseudoregular surface undulation that generally arises as an intermediate stage of heteroepitaxial growth of low misfitting semiconductor layers. This stage is characterized by an interplay of elastic and plastic relaxation processes. The calculations yield (i) the elastic strain energy density distribution and corresponding degree of elastic relaxation and (ii) the shear stress distribution in the glide system, in which misfit dislocations form. As a main result shear stresses due to the crosshatch pattern within the substrate are identified that cause misfit dislocations to multiply in the substrate.

Prior to relaxation of misfit strain by formation of misfit dislocations, a growing heteroepitaxial layer can relax elastically by forming surface undulations called ripples. With increasing amplitude of the ripples the misfit strain and thus stress fields grow markedly inhomogeneous, and dislocation formation may thus be triggered in areas of maximum shear stress. The surface directly above such a new dislocation then represents a band of preferential growth and develops into a ridge, which in turn redistributes the strain in the growing layer. This interwoven elastic/plastic relaxation mechanism can comparably easily be deduced from transmission electron and atomic force microscopy studies of SiGe layers grown onto silicon by liquid phase epitaxy. This growth technique exerts only very small driving forces and thus operates very near thermodynamical equilibrium. The local strain tensor and strain energy density are calculated for the actual layer geometries by three dimensional finite element method and provide for quantification of the mechanism.

The observations of the as-solution-grown GaAs (001) vicinal surfaces yield three kinds of Microtopologies. Each of them develops in a certain range of growth temperature. In a low temperature range (492° C…600° C) we observe parallel growth steps with heights of one Monolayer. In a medium range, a network consisting of two sets of growth steps with larger heights is observed. At high growth temperatures (780° C…850° C) we find growth surfaces that are atomically rough. IMplications of these findings for modelling the crystal growth will be discussed.

Single-crystal Si1−x Gex(O<×≲1) layers are grown by seeded growth on partially SiO2-masked Si-substrates, using a one-step liquid phase epitaxy (LPE) process. The seed regions are stripe- and hole-shaped windows in the oxide, having linear dimensions between 1.5 and 100 μm. The windows extend in different orientation on (111) and (100) orientated substrates. Lateral overgrowth over the oxide-masked areas is achieved up to 70 μm in <110>-directions. X-ray diffraction and Raman scattering show that the epitaxial islands are homogeneous and of excellent crystal quality. In the regions of lateral overgrowth the dislocation density is reduced considerably as shown by defect-etching and cross section transmission electron microscopy.

Although coherent twin boundaries in silicon are electrically inactive, dislocations in the boundaries can act as efficient recombination centers for minority carriers. Different twin boundary dislocation arrangements have been studied by EBIC and TEM. It is found that the observed EBIC contrast is dependent not only on the arrangement of the dislocations in the boundaries but also on the inclination of the boundaries to the surface. It is shown that different defect configurations can produce similar EBIC contrast.