Elastic strain energy of graded Si1−xGex buffer layers

Heigl, G.; Span, G.; Kasper, E.

doi:10.1016/0040-6090(92)90065-j

Cited by 9 publications

(3 citation statements)

References 5 publications

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“…The relaxed Si, _,Ge, alloy buffer layer will, however, contain dislocations to a high density which will extend into the SLS region and reduce the performance of the superlattice. The quality of the buffer layer is governed by elastic-strain-driven phenomena such as dislocation generation and surface waviness [16]. It has been shown during the last years that thick buffers with a step-wise or linearly increasing Ge concentration have an improved crystalline quality and a threading dislocation density almost four orders of magnitude lower than a thin buffer layer.…”

Section: Strain-symmetrized Sige Superlatticesmentioning

confidence: 99%

Photo- and electroluminescence in short-period Si/Ge superlattice structures

Olajos

Engvall

Grimmeiss

et al. 1994

Semicond. Sci. Technol.

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lnterband optical transitions have been studied in a variety of short-period Si/Ge superlattice structures by means of photocurrent spectroscopy, infrared absorption, photo-and electroluminescence. Furthermore, the bandgap photoluminescence from strain-adjusted Si , Ge, (m = 9, 6, 3; n = 6, 4, 2) adjustment was achieved by a thick, step-graded Si,_,Ge, buffer layer resulting in an improved quality of the superlattice with respect to dislocation density. The hydrostatic pressure dependence was modelled using an approach based on deformation potentials and effective-mass theory. In samples annealed at 500 "C and higher, a systematic shifl of the bandgap was observed which is discussed in terms of a process Involving interdiffusion of the Si and Ge atoms. Bandgap-related electroluminescence was observed in mesa diodes at room temperature, whereas the photoluminescence disappeared at about 40 K. The electroluminescence from samples based on different buffer-layer concepts is compared.Apart from the strain-symmetrized Si/Ge superlattices, another structure that has been proposed to act as an efficient, light-emitting device in the Si-based systems is an ultrathin Ge layer (1-2 monolayers) embedded in bulk Si. We report on the electroluminescence spectra at various temperatures from a sample based on this concept, namely a layer sequence consisting of two periods of Si ,,Ge, grown pseudomorphically on an n+ Si substrate. A very intensive, well resolved electroluminescence was obtained at 55 K from the ow.sgper!a!!ices was studied under applied hydrostatic prees~re, The strain

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Section: Strain-symmetrized Sige Superlatticesmentioning

confidence: 99%

Photo- and electroluminescence in short-period Si/Ge superlattice structures

Olajos

Engvall

Grimmeiss

et al. 1994

Semicond. Sci. Technol.

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“…The relief in the compressive stress for the dual stacked sample can be rationalized by the more relaxed structural configuration of the SiO x N y in which the presence of the oxygen atom helps to add flexibility to the nitride film. 17 We suggest that the CBED results obtained for the two samples may be attributed to the minimum free energy criterion based on the theoretical predictions proposed by Matthews in which the total energy of a film material above its critical thickness is given by: [18][19][20] progressively at a small step away from the graded layer/ bulk Si interface and detection was carried out continuously.…”

Section: Resultsmentioning

confidence: 99%

Strain analysis in silicon substrates under uniaxial and biaxial stress by convergent beam electron diffraction

Toh¹,

Loh²,

Boothroyd³

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Articles you may be interested inConvergent beam electron diffraction measurements of relaxation in strained silicon using higher order Laue zone line splitting J. Appl. Phys. 105, 063526 (2009); 10.1063/1.3093693 Direct strain measurement in a 65 nm node strained silicon transistor by convergent-beam electron diffraction Nanoscale strain analysis of strained-Si metal-oxide-semiconductor field effect transistors by large angle convergent-beam electron diffraction Appl. Phys. Lett. 88, 263513 (2006); 10.1063/1.2217136 Nanoscale stress analysis of strained-Si metal-oxide-semiconductor field-effect transistors by quantitative electron diffraction contrast imaging Appl. Phys. Lett. 87, 222111 (2005); 10.1063/1.2135388On the beneficial impact of tensile-strained silicon substrates on the low-frequency noise of n -channel metaloxide-semiconductor transistors A detailed description of the application of the convergent beam electron diffraction ͑CBED͒ technique for studying strain propagation in the Si 1−x Ge x / Si blanket wafers as well as silicon-based metal-oxide-semiconductor field-effect transistors is presented. Specifically, a simple and robust experimental procedure and analysis for silicon lattice strain measurement using the CBED technique is detailed in this article. The use of focused ion beam milling allows for better control of the thickness and site-specific analysis, especially for nanoscaled devices. A pictorial representation of the analytical conditions for the higher order Laue zone lines in CBED patterns is also reported in this work. Based on the Si lattice strain measurement results, we determined that a thin buffer layer of SiO x N y incorporated below the Si 3 N 4 overlay film could render the uniaxial channel strain less compressive. Stress studied on Si 1−x Ge x / Si blanket wafers reveals that a steeper SiGe compositional gradient would induce larger biaxial strain in the underlying Si substrate and hence a smaller amount of misfit dislocations.

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“…However, the Tersoff model does not explain the partial relaxation in the top part of the Ge 1Ϫx Si x graded buffer observed in this study. Heigl et al 21 have dealt with a structure containing both a graded buffer and a uniform buffer. They assumed that once the relaxation occurs, the misfit dislocations would distribute uniformly over the entire thickness of the graded buffer.…”

mentioning

confidence: 99%