GeSn heterostructure micro-disk laser operating at 230 K

Thai, Q. M.; Pauc, N.; Aubin, J.; Bertrand, Mathieu; Chrétien, Jeremie; Delaye, V.; Chelnokov, A.; Hartmann, Jean‐Michel; Reboud, V.; Calvo, V.

doi:10.1364/oe.26.032500

Cited by 82 publications

(64 citation statements)

References 24 publications

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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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“…This energy splitting increases with the Sn content in strain-free GeSn alloys. 3,4 This very attractive feature has been the subject of numerous researches, the aim being to fabricate lasers compatible with group IV elements and complementary metal oxide semiconductor (CMOS) process [5][6][7] which has recently led to an electrically injected source. 8 As the Sn solubility in Ge is limited to only 1 %, i.e.…”

Section: Introductionmentioning

confidence: 99%

Reduced Lasing Thresholds in GeSn Microdisk Cavities with Defect Management of the Optically Active Region

et al. 2020

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GeSn alloys are nowadays considered as the most promising materials to build Group IV laser sources on silicon (Si) in a full complementary metal oxide semiconductorcompatible approach. Recent GeSn laser developments rely on increasing the band structure directness, by increasing the Sn content in thick GeSn layers grown on germanium (Ge) virtual substrates (VS) on Si. These lasers nonetheless suffer from a lack 1 of defect management and from high threshold densities. In this work we examine the lasing characteristics of GeSn alloys with Sn contents ranging from 7 % to 10.5 %. The GeSn layers were patterned into suspended microdisk cavities with different diameters in the 4-8 µm range. We evidence direct band gap in GeSn with 7 % of Sn and lasing at 2-2.3 µm wavelength under optical injection with reproducible lasing thresholds around 10 kW cm −2 , lower by one order of magnitude as compared to the literature. These results were obtained after the removal of the dense array of misfit dislocations in the active region of the GeSn microdisk cavities. The results offer new perspectives for future designs of GeSn-based laser sources.

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“…The first set of GeSn lasers was demonstrated under optically pumping at temperatures up to 90 K [4]. Since then, the studies of GeSn laser have made inspiring leaps in maximum operating temperature (Tmax) up to near-room-temperatures [5][6][7], with expanded wavelength coverage up to 4.6 μm [8], and with reduced thresholds of continuous wave operation [9]. The comparison between ridge waveguide lasers and micro-disk lasers provided further insight into the importance of optical confinement and heat dissipation [10].…”

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confidence: 99%

“…Furthermore, an increase in the Sn composition of the GeSn active region led to lasing at elevated temperatures [6,7]. All these effects were studied under optical pumping.…”

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Electrically injected GeSn lasers on Si operating up to 100 K

Zhou

Miao

Ojo

et al. 2020

Optica

159

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GeSn lasers enable monolithic integration of lasers on the Si platform using all-group-IV directbandgap materials. Although optically pumped GeSn lasers have made significant progress, the study of the electrically injected lasers has just begun only recently. In this work, we present explorative investigations of electrically injected GeSn heterostructure lasers with various layer thicknesses and material compositions. The cap layer total thickness was varied between 240 and 100 nm. At 10 K, a 240-nm-SiGeSn capped device had a threshold current density Jth = 0.6 kA/cm 2 compared to Jth = 1.4 kA/cm 2 of a device with 100-nm-SiGeSn cap due to an improved modal overlap with the GeSn gain region. Both devices had a maximum operating temperature Tmax = 100 K. Device with cap layers of Si0.03Ge0.89Sn0.08 and Ge0.95Sn0.05, respectively, were also compared. Due to less effective carrier (electron) confinement, the device with a 240-nm-GeSn cap had a higher threshold Jth = 2.4 kA/cm 2 and lower maximum operating temperature Tmax = 90 K, compared to those of the 240-nm-SiGeSn capped device with Jth = 0.6 kA/cm 2 and Tmax = 100 K. In the study of the active region material, the device with Ge0.85Sn0.15 active region had a 2.3 higher Jth and 10 K lower Tmax, compared to the device with Ge0.89Sn0.11 in its active region. This is likely due to higher defect density in Ge0.85Sn0.15 rather than an intrinsic issue. The longest lasing wavelength was measured as 2682 nm at 90 K. The investigations provide guidance to the future structure design of GeSn laser diodes to further improve the performance.

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GeSn heterostructure micro-disk laser operating at 230 K

Cited by 82 publications

References 24 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

Reduced Lasing Thresholds in GeSn Microdisk Cavities with Defect Management of the Optically Active Region

Electrically injected GeSn lasers on Si operating up to 100 K

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