Large inherent optical gain from the direct gap transition of Ge thin films
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Kimerling_Large inherent.pdf
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Author(s)
Wang, Xiaoxin
Kimerling, Lionel C.
Michel, Jurgen
Liu, Jifeng
Date Issued
April 2013
Journal
Applied Physics Letters
Publisher
American Institute of Physics (AIP)
Citation
Wang, Xiaoxin et al. “Large Inherent Optical Gain from the Direct Gap Transition of Ge Thin Films.” Applied Physics Letters 102.13 (2013): 131116. © 2013 American Institute of Physics
Version
Final published version
Abstract
The recent demonstration of Ge-on-Si diode lasers renews the interest in the unique carrier dynamics of Ge involving both direct (Γ) and indirect (L) valleys. Here, we report a large inherent direct gap optical gain ≥1300 cm[superscript −1] at room temperature from both tensile-strained n[superscript +] Ge-on-Si films and intrinsic Ge-on-insulator using femtosecond transmittance spectroscopy captured before direct-to-indirect valley scattering. This inherent direct gap gain is comparable to III-V semiconductors. For n[superscript +] Ge, this transient gain is ∼25× larger than its steady state gain, suggesting that reducing Γ→L or enhancing L→Γ intervalley scattering may significantly increase the optical gain of Ge lasers.
MIT Department
MIT Materials Research Laboratory
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Microphotonics Center
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DOI of Published Version
https://doi.org/10.1063/1.4800015
