The electronic band structure of Ge1−xSnxin the full composition range: indirect, direct, and inverted gaps regimes, band offsets, and the Burstein–Moss effect

Polak, Maciej P.; Scharoch, P.; Kudrawiec, R.

doi:10.1088/1361-6463/aa67bf

Cited by 88 publications

(119 citation statements)

References 71 publications

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“…The room-temperature electron mobility increases from 140 cm 2 /Vs in GeSnP1 to 175 cm 2 /Vs in GeSnP3. Since the Sn concentration is the same in all samples, the enhancement of the carrier mobility and the change of the band gap can be associated with the strain engineering and the band gap renormalization, respectively [46,47]. Figure 6b shows the values for the direct band gap  in bulk Ge, tensile stained Ge-on-Si, undoped GeSn and very heavily doped GeSn alloys.…”

Section: Experimental Datamentioning

confidence: 99%

Strain and Band-Gap Engineering in Ge - Sn Alloys via P Doping

et al. 2018

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Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn or ultra-high n-type doping. In this paper, we use all three approaches together -strain engineering, Sn alloying and n-type doping to fabricate direct band gap GeSn alloys. The heavily-doped n-type GeSn was realized using a CMOS-compatible non-equilibrium material processing. P is used to form a highly-doped n-type GeSn layers and to modify the lattice parameter of GeSn:P alloys. The strain engineering in heavily P-doped GeSn films is confirmed by X-ray diffraction and micro-Raman spectroscopy. The change of the band gap in GeSn:P alloy as a function of P concentration is theoretically predicted using density functional theory and experimentally verified by near-infrared spectroscopic ellipsometry.According to the shift of the absorption edge it is shown that for an electron concentration above 1×10 20 cm -3 the band gap renormalization is partially compensated by the Burstein-Moss effect. These results indicate that Ge-based materials have a large potential for the nearinfrared optoelectronic devices, fully compatible with CMOS technology.

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Section: Experimental Datamentioning

confidence: 99%

Strain and Band-Gap Engineering in Ge - Sn Alloys via P Doping

et al. 2018

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“…GeSn alloys can indeed have a direct bandgap under certain conditions of strain and Sn content. Generally, the required Sn contents are far above the Sn solubility in Ge, which is less than 1% . Lasing in GeSn layers has been observed at cryogenic temperature by several research teams It has also been shown that applying tensile strain to GeSn increases the energy splitting between the direct bandgap (Γ valley) and the indirect bandgap (L valley), while simultaneously shifting light emission to longer wavelengths …”

Section: Introductionmentioning

confidence: 99%

“…To calculate band structures of semiconductors, significant number of methods have been developed, such as the pseudopotential, density functional theory (DFT), tight binding, and k·p methods. One advantage of the k·p method is its relative ease of implementation on conventional computers, as it does not require heavy calculation resources.…”

Section: Introductionmentioning

confidence: 99%

Experimental Calibration of Sn‐Related Varshni Parameters for High Sn Content GeSn Layers

et al. 2019

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From temperature-dependent photoluminescence of a single Ge 0.84 Sn 0.16 sample, Sn-related Varshni parameters are extracted and used as input parameters in an 8-band k·p model, and predict direct bandgap energies of high Sn content GeSn alloys with concentration varying from 8% to 16%. Then, exhaustively compared are the calculated direct -valley bandgap energies to photoluminescence results of 13% and 16% Sn content alloys and to direct bandgap energies found in literature. The agreement between k·p modeling and experimental datasets is close to 3% for different strain conditions of GeSn epilayers. The outcome of this study is an 8-band k·p model with a fixed set of parameters, the model being self-sufficient to describe the direct bandgap of Ge 1−x Sn x layers with x varying from 8% to 16% for large ranges of strain and temperature.

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“…The decrease in crystallite size with increase in La 3+ content maybe the possible reason for increase in band gap with increase in La 3+ content. Also, incorporation of La 3+ at the Ba 2+ site increases the density of change carriers, therefore, at room temperature itself many lower energy states in the conduction band may be filled, and subsequently band gap may widen as per the Burstein‐Moss effect . The bottom left inset (II) of Figure shows the room temperature photoluminescence spectra of pristine and La 3+ (2, 4, and 6 at.%) containing barium stannate nanoparticles recorded at an excitation wavelength of 290 nm.…”

Section: Resultsmentioning

confidence: 99%

Cetyltriammonium Bromide Assisted Synthesis of Lanthanum Containing Barium Stannate Nanoparticles for Application in Dye Sensitized Solar Cells

Kumar

Кумар

Quamara

2018

Physica Status Solidi (a)

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In present work, correlation of structural and optical behavior of pristine and lanthanum containing barium stannate nanoparticles (synthesized via cetyltriammonium bromide (CTAB) assisted facile wet chemical route), and its effect on photovoltaic properties of dye-sensitized solar cell are reported. Thermo-gravimetric analysis of the dried compound presumably BaSn(OH) 6 , leads to the formation of BaSnO 3 nanoparticles through three endothermic decomposition processes, via liberation of one mole of water in each step, together with removal of remaining CTAB in initial cycle. The X-ray diffraction patterns reveal that substitution of Ba 2þ lattice sites by La 3þ (upto %6 at.%), the lattice retains its cubic Pm3m symmetry, however, unit cell contracts. The dye sensitized solar cells are fabricated using pristine and La-containing BaSnO 3 as photo anode; platinum coated FTO as counter electrode, N719 dye as sensitizer and I À /I 3 À as electrolyte. These show the highest power conversion efficiency (%9.2%) at the La content of 6 at.% which is about threefold increase in efficiency in comparison to pristine BaSnO 3 . The electron transport properties of these DSSC devices are investigated by electro chemical impedance spectroscopy.

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The electronic band structure of Ge_1−xSn_xin the full composition range: indirect, direct, and inverted gaps regimes, band offsets, and the Burstein–Moss effect

Cited by 88 publications

References 71 publications

Strain and Band-Gap Engineering in Ge - Sn Alloys via P Doping

Strain and Band-Gap Engineering in Ge - Sn Alloys via P Doping

Experimental Calibration of Sn‐Related Varshni Parameters for High Sn Content GeSn Layers

Cetyltriammonium Bromide Assisted Synthesis of Lanthanum Containing Barium Stannate Nanoparticles for Application in Dye Sensitized Solar Cells

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