The influence of the edge effect of the mask on the strain and the morphology of SiGe film grown at the patterned Si substrate by molecular beam epitaxy (original) (raw)
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Dislocation engineering in SiGe heteroepitaxial films on patterned Si (001) substrates
Applied Physics Letters, 2011
We demonstrate dislocation engineering without oxide masks. By using finite element simulations we show how nanopatterning of Si substrates with ͕111͖ trenches provides anisotropic elastic relaxation in a SiGe film, generates preferential nucleation sites for dislocation loops, and allows for dislocation trapping, leaving wide areas free of threading dislocations. These predictions are confirmed by atomic force and transmission electron microscopy performed on overcritical Si 0.7 Ge 0.3 films. These were grown by molecular beam epitaxy on a Si͑001͒ substrate patterned with periodic arrays of selectively etched ͕111͖-terminated trenches.
Strain relaxation and misfit dislocation in SiGe epilayers grown in micron size windows by MBE
Journal of Crystal Growth, 2001
Strain relaxation and misfit dislocation density in Si 0.8Ge 0.2 epilayers grown in micron size windows by MBE are studied. Reduction of misfit dislocation density and increment of strain relaxation in Si 0.8Ge 0.2/Si heterostructure grown by MBE in the windows smaller than 20×20 μm 2 were clearly observed. Besides, experiments showed that dislocation density in SiGe films would be different due to the different stress in the mask materials while the window size and the composition x of the Si xGe 1- x films were the same. Qualitative explanations for these experimental results are discussed.
Interplay of dislocation network and island arrangement in SiGe films grown on Si(001)
Thin Solid Films, 2000
A two-temperature process has been applied to grow 80-nm Si,,,Ge,,, films on Si(OO1) by molecular-beam epitaxy (MBE). The first 30 nm were deposited at a reduced temperature of only 150-200°C (low-temperature stage). The subsequent growth was performed at 550°C, the temperature range conventionally applied for SiGe MBE. Using atomic-force microscopy, we observed that the misfit dislocation network introduced during sample heating after the low-temperature (LT) stage guides the arrangement of {105$-faceted pyramid-like islands. In the case of a very narrow dislocation network ~ induced by ion-assisted growth during the LT stage ~ a checkerboard array of {105$-faceted pits and pyramids evolves with a 'lattice constant' of approximately 200 nm. 0 2000 Elsevier Science B.V. All rights reserved. microscopy 0040-6090/00/$ -see front matter 0 2000 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 0 -6 0 9 0 ( 0 0 ) 0 1 4 6 3 -2
Misfit dislocation gettering by substrate pit-patterning in SiGe films on Si(001)
Applied Physics Letters, 2012
We show that suitable pit-patterning of a Si(001) substrate can strongly influence the nucleation and the propagation of dislocations during epitaxial deposition of Si-rich Si 1-x Ge x alloys, preferentially gettering misfit segments along pit rows. In particular, for a 250 nm layer deposited by molecular beam epitaxy at x Ge ¼ 15%, extended film regions appear free of dislocations, by atomic force microscopy, as confirmed by transmission electron microscopy sampling. This result is quite general, as explained by dislocation dynamics simulations, which reveal the key role of the inhomogeneous distribution in stress produced by the pit-patterning. V C 2012 American Institute of Physics. [http://dx.
Physical Review B, 2002
The morphology, stress, and composition distributions of the crosshatch pattern on a SiGe film grown on a Si͑001͒ substrate using a low-temperature Si buffer are studied by atomic force and Raman microscopies. Crosshatching is not related to composition fluctuation regardless of the stress undulation associated with strain relaxation in the SiGe film. The crosshatch morphology arises from vertical lattice relaxation induced by piled-up misfit dislocations in the Si buffer layer and substrate. A model for crosshatch formation is proposed.
Journal of Electronic Materials, 2013
The quality of germanium (Ge) epitaxial films grown directly on silicon (Si) (001) with 0°and 6°offcut orientation using a reduced-pressure chemical vapor deposition system is studied and compared. Ge film grown on Si (001) with 6°offcut presents $65% higher threading dislocation density and higher root-mean-square (RMS) surface roughness (1.92 nm versus 0.98 nm) than Ge film grown on Si (001) with 0°offcut. Plan-view transmission electron microscopy also reveals that threading dislocations are more severe (in terms of contrast and density) for the 6°offcut. In addition, both high-resolution x-ray diffraction and Raman spectroscopy analyses show that the Ge epilayer on 6°offcut wafer presents higher tensile strain. The poorer quality of the Ge film on Si (001) with 6°offcut is a result of an imbalance in Burgers vectors that favors dislocation nucleation over annihilation.
Strain-relaxed SiGe/Si heteroepitaxial structures of low threading-dislocation density
Thin Solid Films, 2000
A new method of stepwise equilibration for molecular beam epitaxy (MBE) growth of relaxed, low dislocation-density Si 12x Ge x alloy layers on a (001)-Si substrate is presented. The stepwise buffer is prepared in a layer-by-layer manner. The growth of each layer includes two main stages, a low temperature stage and an average-temperature stage, which allows to separate the processes of nucleation and multiplication of mis®t dislocations and the propagation of the threading dislocations. An in situ equilibration annealing at considerably high temperature is implemented before the next growth step to remove the threading dislocations from the layer. The dislocation morphology in these stepwise graded Si 12x Ge x buffers is investigated by transmission electron and atomic force microscopy. The ability to grow fully strain relaxed, almost dislocation-free, virtual substrates of different compositions is demonstrated. q 2000 Published by Elsevier Science S.A. All rights reserved.
Silicon strained layers grown on GaP(001) by molecular beam epitaxy
Journal of Applied Physics, 1985
Mismatch-induced lattice strain in thin Si films grown by molecular beam epitaxy on GaP(OOl) substrates has been measured using transmission electron microscopy, Raman spectroscopy, and Rutherford backscattering. The perpendicular strain in the topmost part of the layers is found to be enhanced in comparison to elasticity theory. Relaxation ofthe strain occurs by the formation of misfit dislocations at significantly larger thickness than predicted by equilibrium theory.