Large inherent optical gain from the direct gap transition of Ge thin films
Author(s)
Wang, Xiaoxin; Kimerling, Lionel C.; Michel, Jurgen; Liu, Jifeng
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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.
Date issued
2013-04Department
MIT Materials Research Laboratory; Massachusetts Institute of Technology. Department of Materials Science and Engineering; Massachusetts Institute of Technology. Microphotonics CenterJournal
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
ISSN
00036951
1077-3118