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Probing scattering mechanisms with symmetric quantum cascade lasers
Christoph Deutsch1, Hermann Detz, Tobias Zederbauer
1Photonics Institute and Center for Micro- and Nanostructures, Vienna University of Technology, Gusshausstrasse 27–29, 1040 Vienna, Austria. christoph.deutsch@tuwien.ac.at
Optics Express
|April 3, 2013
Summary
Symmetric terahertz quantum cascade lasers show bias-dependent performance due to growth asymmetries. Interface roughness scattering significantly impacts device performance, proving crucial for understanding transport and lasing characteristics.
Area of Science:
- Optoelectronics
- Semiconductor Physics
- Quantum Engineering
Background:
- Quantum cascade lasers (QCLs) rely on unipolar carrier transport.
- Nominally symmetric active regions in terahertz QCLs are designed for symmetrical performance under varying bias polarities.
Purpose of the Study:
- To investigate the impact of growth direction asymmetries on the performance of nominally symmetric terahertz quantum cascade lasers.
- To identify and analyze the scattering mechanisms responsible for bias-dependent performance in QCLs.
Main Methods:
- Fabrication of nominally symmetric InGaAs/GaAsSb heterostructures for terahertz quantum cascade lasers.
- Experimental characterization of device performance under different bias polarities.
- Analysis of scattering mechanisms, particularly interface roughness scattering.
Main Results:
- Symmetric devices exhibit strongly bias polarity-dependent performance, deviating from expected symmetry.
- An InGaAs/GaAsSb heterostructure showed significantly better performance under negative bias due to pronounced interface asymmetry.
- Unidirectional device operation was observed, despite a symmetric nominal band structure.
Conclusions:
- Interface asymmetry, specifically interface roughness scattering, plays a critical role in the transport and lasing performance of terahertz quantum cascade lasers.
- Growth direction asymmetries can override nominal band structure symmetry, leading to polarity-dependent device behavior.
- These findings provide experimental evidence for the significant influence of interface scattering on QCL performance.
