Infrared absorption of n-type tensile-strained Ge-on-Si
Name
Kimerling_Infared absorption.pdf
Size
310.22 KB
Format
Adobe PDF
Checksum (MD5)
e87745ea2f34724d86c9e282dd407779
Author(s)
Wang, Xiaoxin
Li, Haofeng
Cai, Yan
Kimerling, Lionel C.
Michel, Jurgen
Liu, Jifeng
Camacho-Aguilera, Rodolfo Ernesto
Date Issued
February 2013
Journal
Optics Letters
Publisher
Optical Society of America
Citation
Wang, Xiaoxin et al. “Infrared Absorption of N-type Tensile-strained Ge-on-Si.” Optics Letters 38.5 (2013): 652. © 2013 Optical Society of America
Version
Final published version
Abstract
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[superscript +] 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 λ[superscript 2]-dependent Drude model of intravalley free-carrier absorption (FCA) breaks down at λ < 15 μm. 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 <20 cm[superscript −1] for n = 4 × 10[superscript 19] cm[superscript −3] at λ = 1.5–1.7 μm, an order lower than the results from Drude model. The strong L → Γ 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 λ[superscript 2]-dependent free-carrier losses of bulk Ge and indicate the great potential for further improvement of Ge-on-Si lasers.
MIT Department
MIT Materials Research Laboratory
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Microphotonics Center
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1364/OL.38.000652
