Germanium-tin explained

Germanium-tin is an alloy of the elements germanium and tin, both located in group 14 of the periodic table. It is only thermodynamically stable under a small composition range. Despite this limitation, it has useful properties for band gap and strain engineering of silicon-integrated optoelectronic and microelectronic semiconductor devices.

Synthesis

Germanium-tin alloys must be kinetically stabilized in order to prevent decomposition.^{[1] [2]} Therefore, low temperature molecular beam epitaxy or chemical vapor deposition techniques are typically used for their synthesis.

Microelectronic applications

Germanium-tin alloys have higher carrier mobilities than either silicon or germanium. Therefore it has been proposed that they can be used as a channel material in high speed metal-oxide-semiconductor field effect transistors.^[3] In addition, the alloys' larger lattice constant relative to germanium makes it possible to use them as stressors to enhance the carrier mobility of germanium channel transistors.^[4]

Optoelectronic applications

At a Sn content beyond approximately 9%, germanium-tin alloys become direct gap semiconductors having efficient light emission suitable for the fabrication of lasers.^[5] Since the constituent elements are chemically compatible with silicon, it is possible to integrate such lasers directly onto silicon microelectronic devices, enabling on-chip optical communication. This is still an active research area, but germanium-tin lasers operating at low temperatures have already been demonstrated.^{[6] [7]} In addition, germanium-tin light emitting diodes operating at room temperature have also been reported.^{[8] [9]}

Notes and References

1. Wirths . S. . Buca . D. . Mantl . S. . Si–Ge–Sn alloys: From growth to applications . Progress in Crystal Growth and Characterization of Materials . Elsevier BV . 62 . 1 . 2016 . 0960-8974 . 10.1016/j.pcrysgrow.2015.11.001 . 1–39.
2. Kouvetakis . J. . Menendez . J. . Chizmeshya . A.V.G. . Tin-Based Group IV Semiconductors: New Platforms for Opto- and Microelectronics on Silicon . . . 36 . 1 . 2006 . 1531-7331 . 10.1146/annurev.matsci.36.090804.095159 . 497–554. 2006AnRMS..36..497K .
3. Loo . R. . Vincent . B. . Gencarelli . F. . Merckling . C. . Kumar . A. . Eneman . G. . Witters . L. . Vandervorst . W. . Caymax . M. . Heyns . M. . Thean . A. . 5. Ge_1−xSn_x Materials: Challenges and Applications . ECS Journal of Solid State Science and Technology . The Electrochemical Society . 2 . 1 . 2012-12-07 . 2162-8769 . 10.1149/2.039301jss . N35–N40. free .
4. Vincent . B. . Shimura . Y. . Takeuchi . S. . Nishimura . T. . Eneman . G. . Firrincieli . A. . Demeulemeester . J. . Vantomme . A. . Clarysse . T. . Nakatsuka . O. . Zaima . S. . Dekoster . J. . Caymax . M. . Loo . R. . 5. Characterization of GeSn materials for future Ge pMOSFETs source/drain stressors . Microelectronic Engineering . Elsevier BV . 88 . 4 . 2011 . 0167-9317 . 10.1016/j.mee.2010.10.025 . 342–346.
5. Gallagher . J. D. . Senaratne . C. L. . Kouvetakis . J. . Menéndez . J. . Compositional dependence of the bowing parameter for the direct and indirect band gaps in Ge_1−ySn_y alloys . Applied Physics Letters . AIP Publishing . 105 . 14 . 2014-10-06 . 0003-6951 . 10.1063/1.4897272 . 142102. 2286/R.I.27074 . free .
6. Web site: Scientists construct the first germanium-tin semiconductor laser for silicon chips. 2015-01-20. Phys.org. 2019-12-12.
7. Web site: The Germanium-Tin Laser: Answer to the On-Chip Data Bottleneck?. 2015-01-22. 2019-12-12. Prachi Patel. IEEE Spectrum.
8. Gallagher . J. D. . Senaratne . C. L. . Sims . P. . Aoki . T. . Menéndez . J. . Kouvetakis . J. . Electroluminescence from GeSn heterostructure pin diodes at the indirect to direct transition . Applied Physics Letters . AIP Publishing . 106 . 9 . 2015-03-02 . 0003-6951 . 10.1063/1.4913688 . 091103. 2015ApPhL.106i1103G . 2286/R.I.29217 . free .
9. Senaratne . C. L. . Wallace . P. M. . Gallagher . J. D. . Sims . P. E. . Kouvetakis . J. . Menéndez . J. . Direct gap Ge_1−ySn_y alloys: Fabrication and design of mid-IR photodiodes . Journal of Applied Physics . AIP Publishing . 120 . 2 . 2016-07-14 . 0021-8979 . 10.1063/1.4956439 . 025701. 2286/R.I.45246 . free .