Nonlinear structure-composition relationships in the Ge<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>y</mml:mi></mml:mrow></mml:msub></mml:math>Sn<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mi>y</mml:mi></mml:msub></mml:math>/Si(100) (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>y</mml:mi><mml:mo>&lt;<

Beeler, Richard T.; Roucka, Radek; Chizmeshya, Andrew; Kouvetakis, John; Menéndez, José

doi:10.1103/physrevb.84.035204

Cited by 62 publications

(42 citation statements)

References 37 publications

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“…The relaxed cubic lattice constant a 0 of the alloy follows from a and c by straightforward application of elasticity theory, as in Ref. 28. The cubic lattice parameter was found to increase smoothly from 5.665 Å to 5.737 Å in the 1-10% Sn composition range, as expected.…”

Section: High-resolution X-ray Diffractionsupporting

confidence: 68%

“…The cubic lattice parameter was found to increase smoothly from 5.665 Å to 5.737 Å in the 1-10% Sn composition range, as expected. 28 The strain component parallel to the interface is defined as e ¼ (a -a 0 )/a 0 . The "as-grown" layers were found to exhibit varying amounts of residual compressive strains (a < a 0 ) from À0.05% to À0.25% depending on composition and growth temperature.…”

Section: High-resolution X-ray Diffractionmentioning

confidence: 99%

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Ge1-ySny (y = 0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties

Senaratne

Gallagher

Jiang

et al. 2014

Journal of Applied Physics

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Novel hydride chemistries are employed to deposit light-emitting Ge1-ySny alloys with y ≤ 0.1 by Ultra-High Vacuum Chemical Vapor Deposition (UHV-CVD) on Ge-buffered Si wafers. The properties of the resultant materials are systematically compared with similar alloys grown directly on Si wafers. The fundamental difference between the two systems is a fivefold (and higher) decrease in lattice mismatch between film and virtual substrate, allowing direct integration of bulk-like crystals with planar surfaces and relatively low dislocation densities. For y ≤ 0.06, the CVD precursors used were digermane Ge2H6 and deuterated stannane SnD4. For y ≥ 0.06, the Ge precursor was changed to trigermane Ge3H8, whose higher reactivity enabled the fabrication of supersaturated samples with the target film parameters. In all cases, the Ge wafers were produced using tetragermane Ge4H10 as the Ge source. The photoluminescence intensity from Ge1−ySny/Ge films is expected to increase relative to Ge1−ySny/Si due to the less defected interface with the virtual substrate. However, while Ge1−ySny/Si films are largely relaxed, a significant amount of compressive strain may be present in the Ge1−ySny/Ge case. This compressive strain can reduce the emission intensity by increasing the separation between the direct and indirect edges. In this context, it is shown here that the proposed CVD approach to Ge1−ySny/Ge makes it possible to approach film thicknesses of about 1 μm, for which the strain is mostly relaxed and the photoluminescence intensity increases by one order of magnitude relative to Ge1−ySny/Si films. The observed strain relaxation is shown to be consistent with predictions from strain-relaxation models first developed for the Si1−xGex/Si system. The defect structure and atomic distributions in the films are studied in detail using advanced electron-microscopy techniques, including aberration corrected STEM imaging and EELS mapping of the average diamond–cubic lattice.

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Section: High-resolution X-ray Diffractionsupporting

confidence: 68%

Section: High-resolution X-ray Diffractionmentioning

confidence: 99%

Ge1-ySny (y = 0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties

Senaratne

Gallagher

Jiang

et al. 2014

Journal of Applied Physics

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“…The resultant in-plane and out-of-plane lattice parameters of the Ge 0.863 Sn 0.137 alloy are measured to be a ¼ 5.7304 Å and c ¼ 5.7836 Å , respectively. These are used to derive (via standard elasticity theory 28 ) a relaxed cubic cell constant a 0 ¼ 5.761 Å , which implies that the strain relaxation reaches 70%. Using the lattice parameter-composition relationship a 0 (y) given in Reference 28, we find that the Sn concentrations are the same as determined directly from RBS.…”

Section: Synthetic Approachmentioning

confidence: 99%

Direct gap Ge1-ySny alloys: Fabrication and design of mid-IR photodiodes

Senaratne

Wallace

Gallagher

et al. 2016

Journal of Applied Physics

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Chemical vapor deposition methods were developed, using stoichiometric reactions of specialty Ge3H8 and SnD4 hydrides, to fabricate Ge1-ySny photodiodes with very high Sn concentrations in the 12%–16% range. A unique aspect of this approach is the compatible reactivity of the compounds at ultra-low temperatures, allowing efficient control and systematic tuning of the alloy composition beyond the direct gap threshold. This crucial property allows the formation of thick supersaturated layers with device-quality material properties. Diodes with composition up to 14% Sn were initially produced on Ge-buffered Si(100) featuring previously optimized n-Ge/i-Ge1-ySny/p-Ge1-zSnz type structures with a single defected interface. The devices exhibited sizable electroluminescence and good rectifying behavior as evidenced by the low dark currents in the I-V measurements. The formation of working diodes with higher Sn content up to 16% Sn was implemented by using more advanced n-Ge1-xSnx/i-Ge1-ySny/p-Ge1-zSnz architectures incorporating Ge1-xSnx intermediate layers (x ∼ 12% Sn) that served to mitigate the lattice mismatch with the Ge platform. This yielded fully coherent diode interfaces devoid of strain relaxation defects. The electrical measurements in this case revealed a sharp increase in reverse-bias dark currents by almost two orders of magnitude, in spite of the comparable crystallinity of the active layers. This observation is attributed to the enhancement of band-to-band tunneling when all the diode layers consist of direct gap materials and thus has implications for the design of light emitting diodes and lasers operating at desirable mid-IR wavelengths. Possible ways to engineer these diode characteristics and improve carrier confinement involve the incorporation of new barrier materials, in particular, ternary Ge1-x-ySixSny alloys. The possibility of achieving type-I structures using binary and ternary alloy combinations is discussed in detail, taking into account the latest experimental and theoretical work on band offsets involving such materials.

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“…After the growth, the Secondary Ion Mass Spectrometry (SIMS), high-resolution X-ray diffraction (HRXRD) 2θ-ω scan and reciprocal space map (RSM) were employed to identify the Si and Sn compositions and the degree of strain of each layer, where the bowing parameter of -0.066 was used. 35 The layer thickness and material quality were examined by cross-sectional transmission electron microscopy (TEM). The HRXRD 2θ-ω scan is shown in Fig.…”

mentioning

confidence: 99%

Direct bandgap type-I GeSn/GeSn quantum well on a GeSn- and Ge- buffered Si substrate

et al. 2018

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This paper reports the comprehensive characterization of a Ge0.92Sn0.08/Ge0.86Sn0.14/Ge0.92Sn0.08 single quantum well. By using a strain relaxed Ge0.92Sn0.08 buffer, the direct bandgap Ge0.86Sn0.14 QW was achieved, which is unattainable by using only a Ge buffer. Band structure calculations and optical transition analysis revealed that the quantum well features type-I band alignment. The photoluminescence spectra showed dramatically increased quantum well peak intensity at lower temperature, confirming that the Ge0.86Sn0.14 quantum well is a direct bandgap material.

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Nonlinear structure-composition relationships in the Ge1−ySny/Si(100) (y<<

Cited by 62 publications

References 37 publications

Ge1-ySny (y = 0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties

Ge1-ySny (y = 0.01-0.10) alloys on Ge-buffered Si: Synthesis, microstructure, and optical properties

Direct gap Ge1-ySny alloys: Fabrication and design of mid-IR photodiodes

Direct bandgap type-I GeSn/GeSn quantum well on a GeSn- and Ge- buffered Si substrate

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