Direct versus indirect optical recombination in Ge films grown on Si substrates

Grzybowski, Gordon; Roucka, Radek; Mathews, Jay; Jiang, Liying; Beeler, Richard T.; Kouvetakis, John; Menéndez, José

doi:10.1103/physrevb.84.205307

Cited by 73 publications

(78 citation statements)

References 30 publications

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“…The simulated curve from [18] of the direct transition shows a good agreement with the undoped reference LED. Higher doping level lead to a peak broadening and increased signals between the direct and indirect transition.…”

Section: Resultssupporting

confidence: 66%

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Electroluminescence of germanium LEDs on silicon: Influence of antimony doping

Schwartz

Klossek

Kittler

et al. 2014

Phys. Status Solidi C

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Antimony‐doped Ge‐LEDs were subjected to electroluminescence studies at temperatures about 300 K and 80 K. The LEDs were grown on Si substrates by MBE. The thickness of the active layer was 300 nm. For the p+nn+‐LEDs the Sb concentrations were 1 × 1018, 1 × 1019, 3 × 1019, 4 × 1019, 7 × 1019 or 1 × 1020 cm–3, respectively. As reference a p+in+‐LED without intentional doping in the active layer was used. The investigated specimen exhibited dominance of the direct transition line at about 0.8 eV. Moreover, luminescence indirect transition was observed. In general, the spectra reveal higher EL intensities at room temperature as compared to 80 K. With decreasing temperature the direct peak was blue shifted. The highest EL intensity was found for the LED with Sb concentration of 3 × 1019 cm–3. With increasing Sb doping a red‐shift of the direct peak was observed, caused by band gap narrowing. In addition, a simulated curve of the direct transition was compared with our samples and fits well with the measured spectra. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Resultssupporting

confidence: 66%

“…So it includes all others influences such as strain or doping. In the lack of own absorption data and data with proper resolution in the observed spectral range the simulated curve of the direct transition from Grzybowski et al [18] was used in this work.…”

Section: Simulation Of the Direct Transitionmentioning

confidence: 99%

Electroluminescence of germanium LEDs on silicon: Influence of antimony doping

Schwartz

Klossek

Kittler

et al. 2014

Phys. Status Solidi C

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“…Unlike most semiconductors, in which PL arises from the lowest band gap, whether direct or indirect, in Ge one sees evidence for both direct and indirect gap emission. [46][47][48] This unique property reflects Germanium's peculiar band structure, in which the direct band gap is only 140 meV above the indirect edge. Even for very small thermal occupation of the conduction band minimum associated with the direct gap, the much higher oscillator strength of the direct optical transition leads to a signal that is comparable to the indirect gap emission, and in fact stronger if reabsorption effects are corrected for or eliminated, as in thin films.…”

Section: Optical Propertiesmentioning

confidence: 99%

“…Figure 11 shows two examples of samples in which the direct and indirect edge are clearly visible. As discussed in prior work, 48,49 the indirect emission is fit with a simple Gaussian and the direct gap emission is fit with an Exponentially Modified Gaussian that accounts from the observed and expected asymmetry of the emission profile. The fit with these functions is indicated as dotted (direct gap) and dash-dotted (indirect gap) lines in the figure.…”

Section: Optical Propertiesmentioning

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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“…The observation of PL in intrinsic films was followed by the study of optical emission in doped n-type films. 47,48 This work led to insights into the origin of the photoluminescence in Ge-like materials grown on Si substrates. The detailed an systematic studies of the PL signal of doped and undoped films made it possible to extract the compositional dependence of both the direct and indirect edges, as shown in Fig.…”

Section: Optical Properties Of Gesn and Gesisn Semiconductorsmentioning

confidence: 99%

Infrared and Terahertz Lasers on SI Using Novel Group-IV Alloys

Menéndez¹,

Kouvetakis²,

Chizmeshya³

et al. 2011

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Direct versus indirect optical recombination in Ge films grown on Si substrates

Cited by 73 publications

References 30 publications

Electroluminescence of germanium LEDs on silicon: Influence of antimony doping

Electroluminescence of germanium LEDs on silicon: Influence of antimony doping

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

Infrared and Terahertz Lasers on SI Using Novel Group-IV Alloys

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