Sensitivity of heterointerfaces on emission wavelength of quantum cascade lasers

The measured emission wavelengths of AlInAs/GaInAs/InP quantum cascade lasers (QCLs) grown by metal organic vapor phase epitaxy (MOVPE) have been reported to be ~ 0.5–1µm longer than the designed QCL wavelength. This work clarifies the origin of the red-shifted wavelength. It was found that AlInAs/G...

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Bibliographic Details
Published in:Journal of crystal growth 2017-04, Vol.464, p.215-220
Main Authors: Wang, C.A., Schwarz, B., Siriani, D.F., Connors, M.K., Missaggia, L.J., Calawa, D.R., McNulty, D., Akey, A., Zheng, M.C., Donnelly, J.P., Mansuripur, T.S., Capasso, F.
Format: Article
Language:English
Subjects:
A1. Interfaces
A1. Segregation
A3. Metalorganic vapor phase epitaxy
A3. Quantum wells
B2. Semiconducting III-V materials
B3. Infrared devices
Band structure
Band structure of solids
Correlation analysis
Emission
Epitaxial growth
Etching
Indium
Lasers
Metalorganic chemical vapor deposition
Quantum cascade lasers
Temperature
Vapor phase epitaxy
Wavelengths
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Summary:The measured emission wavelengths of AlInAs/GaInAs/InP quantum cascade lasers (QCLs) grown by metal organic vapor phase epitaxy (MOVPE) have been reported to be ~ 0.5–1µm longer than the designed QCL wavelength. This work clarifies the origin of the red-shifted wavelength. It was found that AlInAs/GaInAs heterointerfaces are compositionally graded over ~ 2.5–4.5nm, and indium accumulates at the AlInAs-to-GaInAs interface. Thus, the as-grown QCLs are far from the ideal abrupt interfaces used in QCL modeling. When graded layers are incorporated in QCL band structure and wavefunction calculations, the emission wavelengths are red shifted. Furthermore, we demonstrate that QCLs with graded interfaces can be designed without compromising performance and show greatly improved correlation between designed and measured emission wavelength. QCLs were designed for emission between 7.5 and 8.5µm. These structures were grown and wet-etched ridge devices were fabricated. The QCLs exhibit room temperature peak powers exceeding 900mW and pulsed efficiencies of ~8 to 10%. •AlInAs/GaInAs heterointerfaces are compositionally graded.•Indium surface segregation is mainly responsible for compositional grading.•Segregation is evidenced by ex-situ and in-situ characterization.•Grading in quantum cascade lasers leads to red-shifted emission wavelengths.
ISSN:0022-0248
1873-5002
DOI:10.1016/j.jcrysgro.2016.11.029