Crystalline Properties and Strain Relaxation Mechanism of CVD Grown GeSn

Gencarelli, Federica; Vincent, Benjamin; Demeulemeester, Jelle; Vantomme, André; Moussa, Alain; Franquet, Alexis; Kumar, Arul; Bender, Hugo; Meersschaut, Johan; Vandervorst, Wilfried; Loo, Roger; Caymax, Matty; Temst, Kristiaan; Heyns, Marc

doi:10.1149/2.011304jss

Cited by 114 publications

(81 citation statements)

References 27 publications

(25 reference statements)

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“…A gradual reduction of the mean growth rate as the GeSn layer thickness increases is observed, decreasing from 17.6 nm/min for a 158 nm thick layer to 12.8 nm/min for a 970 nm thick layer. This thickness dependent growth rate, observed also in other CVD reactor type 11 , may be linked to an increase in surface roughness, as discussed in the following section.…”

Section: Resultsmentioning

confidence: 56%

“…The most efficient way, in our opinion, to fabricate high quality, partially strain relaxed epilayers is to grow several hundred nanometer thick GeSn layers on Ge virtual substrates (Ge-VS). Significant progress has been made in recent years in epitaxy of these alloys by Chemical Vapor Deposition (CVD) [11][12][13] and Molecular Beam Epitaxy 14,15 . However, the low growth temperatures required for Sn incorporation still lead to an epitaxial breakdown in thick layers due to a strong increase of surface roughness for Sn concentrations > 10 at.% 14 .…”

Section: Introductionmentioning

confidence: 99%

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Direct Bandgap Group IV Epitaxy on Si for Laser Applications

et al. 2015

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The recent observation of a fundamental direct bandgap for GeSn group IV alloys and the demonstration of low temperature lasing provide new perspectives to the fabrication of Si photonic circuits. This work addresses the progress in GeSn alloy epitaxy aiming at room temperature GeSn lasing. Chemical vapor deposition of direct bandgap GeSn alloys with a high -to L-valley energy separation and large thicknesses for efficient optical mode confinement is presented and discussed. Up to 1 µm thick GeSn layers with Sn contents up to 14 at.% were grown on thick relaxed Ge buffers, using Ge 2 H 6 and SnCl 4 precursors. Strong strain relaxation (up to 81 %) at 12.5 at.% Sn concentration, translating into an increased separation between -and L-valleys of about 60 meV, have been obtained without crystalline structure degradation, as revealed by Rutherford backscattering/ion channeling spectroscopy and Transmission Electron Microscopy. Room temperature transmission/reflection and photoluminescence measurements were performed to probe the optical properties of these alloys. The emission/absorption limit of GeSn alloys can be extended up to 3.5 µm (0.35 eV), making those alloys ideal candidates for optoelectronics in the mid-infrared region. Theoretical net gain calculations indicate that large room temperature laser gains should be reachable even without additional doping.

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Section: Resultsmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Direct Bandgap Group IV Epitaxy on Si for Laser Applications

et al. 2015

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“…An additional advantage of using Ge buffer layers is that the predicted Type-I band alignment 19 between Ge and Ge 1Ày Sn y would effectively confine the photoexcited electron-hole pairs to the Ge 1-y Sn y layer, far away from the highly defected Ge/Si interface. On the other hand, while the critical thickness for pseudomorphic growth of Ge 1Ày Sn y on Si corresponds to a few atomic layers, all but insuring full strain relaxation in the growing film, the corresponding critical thickness value for growth on Ge is much higher, 20 raising the possibility of a substantial amount of compressive strain in the films. In fact, fully pseudomorphic Ge/Ge 1Ày Sn y interfaces have been demonstrated by several groups.…”

Section: Introductionmentioning

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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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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“…Different bowing values were published for GeSn alloys. Kouvetakis et al extracted it to be h GeSn ¼ 0.0468 Å , and Gencarelli et al 27 calculated it out to be h GeSn ¼ 0.041 Å . Here, we use the bowing value of 0.0468 Å .…”

Section: Elastic Theory Model For Stress Induced Changes In the Omentioning

confidence: 99%

Optical properties of pseudomorphic Ge1−xSnx (x = 0 to 0.11) alloys on Ge(001)

Medikonda¹,

Muthinti²,

Vasić³

et al. 2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The characterization of the optical properties of pseudomorphic Ge1−xSnx/Ge/Si (x = 0 to 0.11) alloys from the IR to UV is presented. The Ge1−xSnx alloys were epitaxially grown on relaxed Ge grown on Si. Rutherford backscattering (RBS) and RBS ion channeling methods were used to confirm the Sn composition and substitutional nature of the Sn into the Ge lattice. The pseudomorphic nature of the Ge1−xSnx on Ge is confirmed using high resolution x-ray diffraction (HRXRD) and transmission electron microscopy. Although HRXRD reciprocal space maps indicated that the Ge1−xSnx was pseudomorphic to Ge, the shape of the Bragg peaks indicated that the sample surface was rough. The rough surface morphology is confirmed using atomic force microscopy. The complex dielectric function is reported in the IR, visible, and UV spectrum in the wavelength range of 0.2–5.06 eV. The E1, E1 + Δ1, E2, and E0 critical points are extracted using second and third derivative line shape fitting and are compared with the elastic theory calculations of strained Ge1−xSnx (x = 0 to 0.11) alloys and fully relaxed Ge1−xSnx (x = 0 to 0.11) alloys. The E0 critical point energies are observed to have slightly larger values than those calculated for completely relaxed Ge1−xSnx alloys due to the presence of compressive strain.

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Crystalline Properties and Strain Relaxation Mechanism of CVD Grown GeSn

Cited by 114 publications

References 27 publications

Direct Bandgap Group IV Epitaxy on Si for Laser Applications

Direct Bandgap Group IV Epitaxy on Si for Laser Applications

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

Optical properties of pseudomorphic Ge1−xSnx (x = 0 to 0.11) alloys on Ge(001)

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