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Optics Letters

Optics Letters


  • Editor: Alan E. Willner
  • Vol. 38, Iss. 5 — Mar. 1, 2013
  • pp: 652–654

Infrared absorption of n-type tensile-strained Ge-on-Si

Xiaoxin Wang, Haofeng Li, Rodolfo Camacho-Aguilera, Yan Cai, Lionel C. Kimerling, Jurgen Michel, and Jifeng Liu  »View Author Affiliations

Optics Letters, Vol. 38, Issue 5, pp. 652-654 (2013)

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We analyze the IR absorption of tensile-strained, n-type Ge for Si-compatible laser applications. A strong intervalley scattering from the indirect L valleys to the direct Γ valley in n+ Ge-on-Si is reported for the first time to our knowledge. The intervalley absorption edge is in good agreement with the theoretical value. On the other hand, we found that the classical λ2-dependent Drude model of intravalley free-carrier absorption (FCA) breaks down at λ<15μm. A first-principle model has to be employed to reach a good agreement with the experimental data. The intravalley FCA loss is determined to be <20cm1 for n=4×1019cm3 at λ=1.51.7μm, an order lower than the results from Drude model. The strong LΓ intervalley scattering favors electronic occupation of the direct Γ valley, thereby enhancing optical gain from the direct gap transition of Ge, while the low intravalley free-electron absorption at lasing wavelengths leads to low optical losses. These two factors explain why the first electrically pumped Ge-on-Si laser achieved a higher net gain than the theoretical prediction using λ2-dependent free-carrier losses of bulk Ge and indicate the great potential for further improvement of Ge-on-Si lasers.

© 2013 Optical Society of America

OCIS Codes
(130.3130) Integrated optics : Integrated optics materials
(160.3380) Materials : Laser materials
(250.5960) Optoelectronics : Semiconductor lasers

ToC Category:
Integrated Optics

Original Manuscript: January 3, 2013
Manuscript Accepted: January 21, 2013
Published: February 22, 2013

Xiaoxin Wang, Haofeng Li, Rodolfo Camacho-Aguilera, Yan Cai, Lionel C. Kimerling, Jurgen Michel, and Jifeng Liu, "Infrared absorption of n-type tensile-strained Ge-on-Si," Opt. Lett. 38, 652-654 (2013)

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