Optically pumped GeSn micro-disks with 16% Sn lasing at 3.1 <i>μ</i>m up to 180 K

Reboud, V.; Gassenq, A.; Pauc, N.; Aubin, J.; Milord, Laurent; Thai, Q. M.; Bertrand, Mathieu; Guilloy, Kévin; Rouchon, D.; Rothman, J.; Zabel, T.; Pilon, Francesco Armand; Sigg, H.; Chelnokov, A.; Hartmann, J.-M.; Calvo, V.

doi:10.1063/1.5000353

Cited by 176 publications

(132 citation statements)

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“…The most successful route for laser action within group IV materials nowadays is based on germanium-tin (GeSn) semiconductors. The first demonstration of an optically pumped laser 3 and subsequent developments to improve the performance in respect to threshold and operation temperature [4][5][6][7] , have shown the potential of these group IV materials for achieving Si-based light sources, the final ingredient for completing an all-inclusive nano-photonic CMOS platform. Furthermore, (Si)GeSn materials can help to extend the present Si photonics platform with a much broader application area than only near infrared data communication.…”

Section: Introductionmentioning

confidence: 99%

Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys

et al. 2020

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GeSn alloys are the most promising semiconductors for light emitters entirely based on group IV elements. Alloys containing more than 8 at. % Sn have fundamental direct band-gaps, similar to conventional III-V semiconductors and thus can be employed for light emitting devices. Here, we report on GeSn microdisk lasers encapsulated with a SiN x stressor layer to produce tensile strain. A 300 nm GeSn layer with 5.4 at. % Sn, which is an indirect band-gap semiconductor as-grown with a compressive strain of −0.32 %, is transformed via tensile strain engineering into a truly direct band-gap semiconductor. In this approach the low Sn concentration enables improved defect engineering and the tensile strain delivers a low density of states at the valence band edge, which is the light hole band. Continuous wave (cw) as well as pulsed lasing are observed at very low optical pump powers. Lasers with emission wavelength of 2.5 µm have thresholds as low as 0.8 kW cm −2 for ns-pulsed excitation, and 1.1 kW cm −2 under cw excitation. These thresholds are more than two orders of magnitude lower than those previously reported for bulk GeSn lasers, approaching these values obtained for III-V lasers on Si. The present results demonstrate the feasabiliy and are the guideline for monolithically integrated Si-based laser sources on Si photonics platform. arXiv:2001.04927v1 [physics.app-ph] 14 Jan 2020 at an Sn concentration of 8 at. % 3 . The lattice mismatch between Sn-containing alloys and the Ge buffer layer, the typical virtual substrate for their epitaxial growth, generates compressive strain in the grown layer, which counteracts the effect of Sn incorporation, decreasing the directness ∆E L−Γ = E L − E Γ . On the contrary, applying tensile strain will increase the directness. Finding a proper balance between a moderate Sn content to minimize crystal defects and to maintain thermal stability of the GeSn alloy on one hand and making use of tensile strain on the other hand are the keys to bring lasing threshold and operation temperature close to application's requirements. The mainstream research to increase ∆E L−Γ focuses on high Sn content alloys 5, 12 , obtained by epitaxy of thick strain-relaxed GeSn layers. A large directnesss is obtained, leading to higher temperature operation, although at the expense of steadily increasing laser threshold 13 . We have recently theoretically proposed an alternative approach, which is based on two key ingredients: employing moderate Sn content GeSn alloys, and inducing tensile strain in them 14 . This study indicated that, if a given directness is reached via tensile strain rather than by increasing Sn content, the material can provide a higher net gain. The underlying physics originates in the valence band splitting and lifting up of the light hole, LH, band above the heavy hole, HH, band. Its lower density of states (DOS) reduces the carrier density required for transparency, hence reduces the lasing threshold, as will be shown below. GeSn alloys with a moderate Sn content offer a couple of ...

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Section: Introductionmentioning

confidence: 99%

Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys

et al. 2020

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“…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%

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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“…[2][3][4] Nonetheless, in order to move toward real-market applications, several issues still have to be addressed such as the low laser operating temperature. In particular, an increase of the Sn content in the active material beyond ∼12 at.…”

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confidence: 99%

The thermal stability of epitaxial GeSn layers

et al. 2018

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We report on the direct observation of lattice relaxation and Sn segregation of GeSn/Ge/Si heterostructures under annealing. We investigated strained and partially relaxed epi-layers with Sn content in the 5 at. %-12 at. % range. In relaxed samples, we observe a further strain relaxation followed by a sudden Sn segregation, resulting in the separation of a β-Sn phase. In pseudomorphic samples, a slower segregation process progressively leads to the accumulation of Sn at the surface only. The different behaviors are explained by the role of dislocations in the Sn diffusion process. The positive impact of annealing on optical emission is also discussed.

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Optically pumped GeSn micro-disks with 16% Sn lasing at 3.1 μm up to 180 K

Cited by 176 publications

References 40 publications

Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys

Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys

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

The thermal stability of epitaxial GeSn layers

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