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


Strained GeSn alloys are promising for realizing light emitters based entirely on group IV elements. Here, we report GeSn microdisk lasers encapsulated with a SiNx stressor layer to produce tensile strain. A 300 nm-thick GeSn layer with 5.4 at% Sn, which is an indirect-bandgap semiconductor as-grown, is transformed via tensile strain engineering into a direct-bandgap semiconductor that supports lasing. 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. We observe ultra-low-threshold continuous-wave and pulsed lasing at temperatures up to 70 K and 100 K, respectively. Lasers operating at a wavelength of 2.5 μm have thresholds of 0.8 kW cm−2 for nanosecond pulsed optical excitation and 1.1 kW cm−2 under continuous-wave optical excitation. The results offer a path towards monolithically integrated group IV laser sources on a Si photonics platform.

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Fig. 1: Structural and optical characterization.
Fig. 2: Continuous-wave lasing from GeSn.
Fig. 3: Carrier density at threshold and net gain.
Fig. 4: Pulsed laser.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

Code availability

Finite-element modelling was performed using commercially available COMSOL software. All other calculation codes were used in published works where model details are provided. The codes are not publicly available; any requests should be sent to the corresponding authors.


  1. Soref, R. A., Buca, D. & Yu, S.-Q. Group IV photonics—driving integrated optoelectronics. Opt. Photon. News 27, 32–39 (2016).

    Article  ADS  Google Scholar 

  2. Thomson, D. et al. Roadmap on silicon photonics. J. Opt. 18, 073003 (2016).

    Article  ADS  Google Scholar 

  3. Wirths, S. et al. Lasing in direct-bandgap GeSn alloy grown on Si. Nat. Photon. 9, 88–92 (2015).

    Article  ADS  Google Scholar 

  4. Stange, D. et al. Optically pumped GeSn microdisk lasers on Si. ACS Photon. 3, 1279–1285 (2016).

    Article  Google Scholar 

  5. Reboud, V. et al. Optically pumped GeSn micro-disks with 16% Sn lasing at 3.1 μm up to 180 K. Appl. Phys. Lett. 111, 092101 (2017).

    Article  ADS  Google Scholar 

  6. Al-Kabi, S. et al. An optically pumped 2.5 μm GeSn laser on Si operating at 110 K. Appl. Phys. Lett. 109, 171105 (2016).

    Article  ADS  Google Scholar 

  7. Thai, Q. M. et al. GeSn heterostructure micro-disk laser operating at 230 K. Opt. Express 26, 32500–32508 (2018).

    Article  ADS  Google Scholar 

  8. Hodgkinson, J. & Tatam, R. P. Optical gas sensing: a review. Meas. Sci. Technol. 24, 012004 (2013).

    Article  ADS  Google Scholar 

  9. Sieger, M. & Mizaikoff, B. Toward on-chip mid-infrared sensors. Anal. Chem. 88, 5562–5573 (2016).

    Article  Google Scholar 

  10. Singh, V. et al. Mid-infrared materials and devices on a Si platform for optical sensing. Sci. Technol. Adv. Mater. 15, 014603 (2014).

    Article  Google Scholar 

  11. Razeghi, M. & Nguyen, B.-M. Advances in mid-infrared detection and imaging: a key issues review. Rep. Prog. Phys. 77, 82401 (2014).

    Article  Google Scholar 

  12. Dou, W. et al. Optically pumped lasing at 3 μm from compositionally graded GeSn with tin up to 22.3%. Opt. Lett. 43, 4558–4561 (2018).

    Google Scholar 

  13. Zhou, Y. et al. Optically pumped GeSn lasers operating at 270 K with broad waveguide structures on Si. ACS Photon. 6, 1434–1441 (2019).

    Article  Google Scholar 

  14. Rainko, D. et al. Impact of tensile strain on low Sn content GeSn lasing. Sci. Rep. 9, 259 (2019).

    Article  ADS  Google Scholar 

  15. Gencarelli, F. et al. Crystalline properties and strain relaxation mechanism of CVD grown GeSn. ECS Trans. 50, 875–883 (2013).

    Article  Google Scholar 

  16. Dou, W. et al. Investigation of GeSn strain relaxation and spontaneous composition gradient for low-defect and high-Sn alloy growth. Sci. Rep. 8, 5640 (2018).

    Article  ADS  Google Scholar 

  17. Stange, D. et al. GeSn/SiGeSn heterostructure and multi quantum well lasers. ACS Photon. 5, 4628–4636 (2018).

    Article  Google Scholar 

  18. Du, W. et al. Study of Si-based GeSn optically pumped lasers with micro-disk and ridge waveguide structures. Front. Phys. 7, 147 (2019).

    Article  Google Scholar 

  19. Minamisawa, R. et al. Top-down fabricated silicon nanowires under tensile elastic strain up to 4.5%. Nat. Commun. 3, 1096 (2012).

    Article  ADS  Google Scholar 

  20. El Kurdi, M. et al. Direct band gap germanium microdisks obtained with silicon nitride stressor layers. ACS Photon. 3, 443–448 (2016).

    Article  Google Scholar 

  21. Virgilio, M., Manganelli, C. L., Grosso, G., Pizzi, G. & Capellini, G. Radiative recombination and optical gain spectra in biaxially strained n-type germanium. Phys. Rev. B 87, 235313 (2013).

    Article  ADS  Google Scholar 

  22. Bao, S. et al. Low-threshold optically pumped lasing in highly strained germanium nanowires. Nat. Commun. 8, 1845 (2017).

    Article  ADS  Google Scholar 

  23. Süess, M. J. et al. Analysis of enhanced light emission from highly strained germanium microbridges. Nat. Photon. 7, 466–472 (2013).

    Article  ADS  Google Scholar 

  24. Armand Pilon, F. T. et al. Lasing in strained germanium microbridges. Nat. Commun. 10, 2724 (2019).

    Article  ADS  Google Scholar 

  25. Ghrib, A. et al. Control of tensile strain in germanium waveguides through silicon nitride layers. Appl. Phys. Lett. 100, 201104 (2012).

    Article  ADS  Google Scholar 

  26. Capellini, G. et al. Strain analysis in SiN/Ge microstructures obtained via Si-complementary metal oxide semiconductor compatible approach. J. Appl. Phys. 113, 013513 (2013).

    Article  ADS  Google Scholar 

  27. von den Driesch, N. et al. Direct bandgap group IV epitaxy on Si for laser applications. Chem. Mater. 27, 4693–4702 (2015).

    Article  Google Scholar 

  28. Ghrib, A. et al. All-around SiN stressor for high and homogeneous tensile strain in germanium microdisk cavities. Adv. Opt. Mater. 3, 353–358 (2015).

    Article  Google Scholar 

  29. Zaumseil, P. et al. The thermal stability of epitaxial gesn layers. Appl. Phys. Lett. Mater. 6, 076108 (2018).

    Google Scholar 

  30. Elbaz, A. et al. Solving thermal issues in tensile-strained Ge microdisks. Opt. Express 26, 28376–28384 (2018).

    Article  ADS  Google Scholar 

  31. Elbaz, A. et al. Germanium microlasers on metallic pedestals. APL Photon. 3, 106102 (2018).

    Article  ADS  Google Scholar 

  32. Uchida, N. et al. Carrier and heat transport properties of polycrystalline GeSn films on SiO2. Appl. Phys. Lett. 10, 232105 (2015).

    Article  ADS  Google Scholar 

  33. Pezzoli, F., Giorgioni, A., Patchett, D. & Myronov, M. Temperature-dependent photoluminescence characteristics of GeSn epitaxial layers. ACS Photon. 3, 2004–2009 (2016).

    Article  Google Scholar 

  34. Cheng, R. et al. Relaxed and strained patterned germanium-tin structures: a Raman scattering study. ECS J. Solid State Sci. Technol. 2, P138–P145 (2013).

    Article  Google Scholar 

  35. Rabolt, J. F. & Bellar, R. The nature of apodization in Fourier transform spectroscopy. Appl. Spectrosc. 35, 132–135 (1981).

    Article  ADS  Google Scholar 

  36. El Kurdi, M. et al. Tensile-strained germanium microdisks with circular Bragg reflectors. Appl. Phys. Lett. 108, 091103 (2016).

    Article  ADS  Google Scholar 

  37. Sargent, M. Theory of a multimode quasiequilibrium semiconductor laser. Phys. Rev. A 48, 717–726 (1993).

    Article  ADS  Google Scholar 

  38. Stange, D. et al. Short-wave infrared leds from GeSn/SiGeSn multiple quantum wells. Optica 4, 185–188 (2017).

    Article  ADS  Google Scholar 

  39. Ghrib, A. et al. Tensile-strained germanium microdisks. Appl. Phys. Lett. 102, 221112 (2013).

    Article  ADS  Google Scholar 

  40. Prost, M. et al. Tensile-strained germanium microdisk electroluminescence. Opt. Express 23, 6722–6730 (2015).

    Article  ADS  Google Scholar 

  41. Wang, Z. et al. Novel light source integration approaches for silicon photonics. Laser Photon. Rev. 11, 1700063 (2017).

    Article  ADS  Google Scholar 

  42. Seifried, M. et al. Monolithically integrated CMOS-compatible III–V on silicon lasers. IEEE J. Select. Top. Quant. Electron. 24, 1–9 (2018).

    Article  MathSciNet  Google Scholar 

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M.E.K. and A.E. thank R. Colombelli and A. Bousseksou for discussions and their help with mounting the PL set-up with the FTIR spectrometer. We thank G. Mussler for XRD measurements. This work used knowledge acquired in the collaboration with H. Sigg from PSI. This work was supported by the French RENATECH network, the French National Research Agency (Agence Nationale de la Recherche, ANR) through funding of the ELEGANTE project (ANR-17-CE24-0015) and the Deutsche Forschungsgemeinschaft (DFG) via the project ‘SiGeSn Laser for Silicon Photonics’. A.E. was supported by ANRT through a CIFRE grant. A.F. acknowledges funding within the ANR-16-CE09-0029-03 TIPTOP project.

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Authors and Affiliations



All authors contributed to the work. P.B., M.E.K. and A.E. designed the device structure. M.E.K. and A.E. performed the strained disks fabrication with E.H., I.S., K.P. and G.P. M.E.K. and A.E. performed the PL measurements and laser experiments with N.Z. and X.C. K.P., G.P., I.S., N.v.d.D. and D.B. performed the structural analysis of the material. The GeSn layer was grown by D.B. and N.v.d.D. on substrates from J.-M.H. The Raman analyses were performed by A.F. and R.O. P.B., S.S. and Z.I. contributed to the modelling with M.E.K. and D.B. The work was supervised by D.G., F.B., P.B., D.B. and M.E.K. P.B., M.E.K., N.v.d.D., D.G. and D.B. wrote the manuscript.

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Correspondence to Dan Buca or Moustafa El Kurdi.

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Elbaz, A., Buca, D., von den Driesch, N. et al. Ultra-low-threshold continuous-wave and pulsed lasing in tensile-strained GeSn alloys. Nat. Photonics 14, 375–382 (2020).

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