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Salvador, D. De; Петрович, Милешко Леонид; Berti, M.; Romanato, Filippo; Napolitani, E.; Drigo, A. V.; Stangl, J.; Zerlauth, S.; Mühlberger, M.; Schäffler, F.; Bauer, G.; Kelires, P. C.

doi:10.1103/physrevb.61.13005

Cited by 80 publications

(46 citation statements)

References 35 publications

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“…The large compressive strain in the quantum wells results in a considerable splitting of the light and heavy-hole exciton peaks. In order to reproduce this splitting we have revised our choice of the uniaxial model solid deformation potential used in the bandstructure calculations so that we have b ¼ 2:86 eV [13], together with a larger lattice bowing parameter of 0:026 nm [14]. These parameters also provide agreement with the experimental data from [3].…”

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confidence: 66%

Modulation of the absorption coefficient at 13 μm in Ge/SiGe multiple quantum well heterostructures on silicon

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Myronov

et al. 2011

Opt. Lett.

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We report modulation of the absorption coefficient at 1:3 μm in Ge/SiGe multiple quantum well heterostructures on silicon via the quantum-confined Stark effect. Strain engineering was exploited to increase the direct optical bandgap in the Ge quantum wells. We grew 9 nm-thick Ge quantum wells on a relaxed Si 0:22 Ge 0:78 buffer and a contrast in the absorption coefficient of a factor of greater than 3.2 was achieved in the spectral range 1290-1315 nm. © 2011 Optical Society of America OCIS codes: 230.4110, 230.4205, 250.4110, 250.5590, 260.6580. Existing silicon Mach-Zehnder modulators that exploit the carrier dispersion effect are typically either large and dissipate considerable amounts of power [1] or require the use of resonant cavities, which have temperature stabilization issues and are very sensitive to fabrication tolerances. The development of silicon-based electroabsorption modulators (EAMs) is desirable for emerging silicon photonics applications, including optical network interconnects and fibre-to-the-home, because such devices can have a small footprint, low power consumption, and good temperature stability. Several optical fiber telecommunications systems exploit the spectral 'window' around 1:3 μm, which corresponds to zero dispersion in standard single-mode fibers. In particular, some passive optical network (PON) architectures use 1:3 μm radiation for upstream signals [2]. Therefore, it is desirable to fabricate optical modulators that can operate at this wavelength. Ge/SiGe multiple quantum well (MQW) heterostructures can be epitaxially grown on silicon wafers using a relaxed buffer layer (see, e.g., [3]), where the alternating layers should be strain-balanced to the buffer layer so that no net strain accumulates in the MQW stack. Previous studies of the quantum-confined Stark effect (QCSE) in Ge/SiGe MQW structures have reported buffers layers with a Ge fraction of 90% or more [4][5][6][7]. Here, we describe absorption spectra for a strain-balanced stack of ten 9 nm thick Ge quantum wells and eleven 7 nm thick Si 0:4 Ge 0:6 barriers grown on a relaxed Si 0:22 Ge 0:78 buffer. The large compressive strain in the Ge quantum wells results in an increase in the direct bandgap compared with relaxed Ge, which results in a blue-shift of the absorption edge, and proper choice of the layer widths and compositions allows us to control the absorption edge of the structure [8].The MQW heterostructures were grown using reduced pressure chemical vapor deposition (RP-CVD) on a relaxed Si 0:22 Ge 0:78 buffer. The buffer was grown using reverse linear grading (RLG) from a relaxed Ge seed layer, which was grown on an Si substrate [9]. Further details of the epitaxial growth can be found in [10]. Circular mesa devices of 80 μm diameter were defined using optical lithography and reactive-ion etching and a Ti/Al metal stack was deposited and sintered at 400°C for 30 minutes to form electrical contacts. A schematic diagram of the cross section of the devices is shown in Fig. 1.Absorption spectra were inferred f...

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confidence: 66%

Modulation of the absorption coefficient at 13 μm in Ge/SiGe multiple quantum well heterostructures on silicon

Lever

Myronov

et al. 2011

Opt. Lett.

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“…In the FEM model, we consider the nonlinear lattice parameter variation with Ge content as obtained in Ref. 33. The elastic constants are interpolated linearly between the values of Si and Ge, 34 taking into account the slight elastic anisotropies.…”

Section: Analysis Of Strain and Compositionmentioning

confidence: 99%

Beyond the ensemble average: X-ray microdiffraction analysis of single SiGe islands

et al. 2008

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X-ray microdiffraction is used to analyze strain and composition profiles in individual micron-sized SiGe islands grown by liquid phase epitaxy on Si͑001͒ substrates. From the variation of the scattered intensity while scanning the sample through a focused x-ray beam of few m size, an image of the island distribution on the sample is created. Using this image it is possible to identify particular islands and select them for analysis one by one. The Ge and strain distribution within each island is obtained from the intensity distribution in reciprocal space measured for several individual islands. The detailed shape of each measured island is obtained from scanning electron microscopy. Apart from truncated pyramid-shaped islands, we detect and characterize a small number of flat islands and show that they represent an earlier growth stage of the pyramidal shaped ones. This analysis is only possible by combining the local x-ray diffraction with scanning electron microscopy on exactly the same islands.

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“…X'Pert epitaxy and X'Pert reflectivity are used to model the rocking curve and reflectivity measurements. In modelling the rocking curve data, the built-in model utilizing a mixture of Si, Ge and diamond with bowing corrections [5] is used. The extraction of carbon concentration from the free lattice parameter of the modelled structure can differ from the built-in model and will be discussed later.…”

Section: Structural Characterizationmentioning

confidence: 99%