In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2016-02, No. 30 ( 2016-09-01), p. 1939-1939
Abstract:
Group IV semiconductors attract intensive interests for potential monolithically integrated photonics on the Si platform. The realization of Group IV-based light emitters is challenging yet highly desirable. Ge-on-Si lasing from the direct gap transition has been demonstrated at room temperature by employing n-type doping and tensile strain to reduce the energy difference between direct bandgap and indirect bandgap[1-2]. An alternative method is incorporating Sn into Ge, which shrinks the direct bandgap much faster than the indirect bandgap, thereby leading to direct bandgap GeSn alloys. We found that the incorporation of Sn into Ge can also enhance the crystallization of GeSn on amorphous substrate, which is beneficial for 3D photonic integration on Si by moving all the photonic components to the metal/dielectric interconnect level well above the CMOS layer using back-end-of-line (BEOL) processing. In our previous work, high crystallinity GeSn substitutional alloy thin films with up to 9 at.% Sn are directly grown on amorphous SiO 2 layers at low crystallization temperatures of 370~470 °C, eliminating the thick buffer layer commonly used in epitaxial GeSn on Si.[3] Recently, epitaxial GeSn-based lasing is reported in the near mid-infrared wavelength range, but only observed at low temperatures [4]. A detailed understanding of the ultrafast carrier dynamics is necessary to design and optimize high-performance GeSn lasers operating at room temperature. In this study, we investigate the power-dependent femtosecond transient gain of direct-gap GeSn with 9% Sn thin films crystallized on amorphous SiO 2 layers in the wavelength range of 1950~2350 nm. It is found at carrier injection density Δn 〈 1×10 17 cm -3 , the transmission of GeSn is same as that measured by Fourier Transfer Infrared spectroscopy (FTIR), i.e. no optical bleaching. When the injection density is increased to Δn~8×10 18 cm -3 , the GeSn film becomes transparent at λ~2000 nm. At higher injection of Δn~2×10 19 cm -3 , net transient gain is observed at λ=1900-2150 nm, with a peak gain of 6300 cm -1 at λ=2000 nm . Further increasing the carrier injection to Δn~1×10 20 cm -3 , the peak of transient gain red-shifted to 2100 nm due to the bandgap renormalization, and the peak gain further increases to ~8000 cm -1 . The transient gain of GeSn with 9% Sn is similar to III-V direct bandgap semiconductors at similar injection levels. These results confirm that the GeSn thin film crystalized on amorphous SiO2 is a good optical gain medium. Further studies will reveal more detailed carrier dynamics between direct and indirect conduction valleys. [1] R. E. Camacho-Aguilera, Y. Cai, N. Patel, J. T. Bessette, M. Romagnoli, L. C. Kimerling, and J. Michel, Opt. Express . 20, 11316 (2012). [2] R. Koerner, M. Oehme, M. Gollhofer, et al, Opt. express, 23, 14815 (2015). [3] H. Li, J. Brouillet, A. Salas, X. Wang and J. Liu, Opt. Mater. Express 3, 1385 (2013). [4] S.Wirths, R. Geiger, N.von den Diresch, et al, Nature Photonics, 9, 88 (2015).
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2016-02/30/1939
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2016
detail.hit.zdb_id:
2438749-6
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