2017 Fiscal Year Research-status Report
Terahertz quantum cascade lasers based on (GaN)m/(AlN)n monolayer superlattices in order to exploit their potential for high temperature operation
| Project/Area Number |
17K14113
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
王 科 国立研究開発法人理化学研究所, 光量子工学研究領域, 研究員 (60532223)
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | 結晶工学 / THz QCL / MBE / GaN |
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| Outline of Annual Research Achievements |
One paper will be soon published on JJAP. "Controlling loss of waveguides for potential GaN terahertz quantum cascade lasers by tuning the plasma frequency of doped layers", by Ke Wang*, et al. and H. Hirayama (in press).
One paper is submitted to APL and under review. "Broadening mechanisms and self-consistent gain calculations for GaN quantum cascade laser structures", by Ke Wang, et al, and H. Hirayama.
One paper is accepted by Journal of Infrared and Millimeter Waves, "High output power THz Quantum Cascade Lasers and their temperature dependent performance", by Tsung-Tse Lin*, Ke Wang, Li Wang and Hideki Hirayama.
I have given one talk (APWS) and one poster presentations (ITQW) in international conferences, and two oral presentations in Obutsu. And submitted an abstract to IQCLSW 2018.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
First of all, for GaN THz QCL, the waveguide design is very important. I have systematically investigated the possible waveguides for GaN THz QCLs. The calculations indicate that the double metal waveguide (DMW) is the best. A new strategy for removing the substrate for DMW processing has been developed. On MOCVD grown AlGaN/Si templates, thick QCL layers more than 5 micrometers with good quality have been grown already.
I also developed a new design tool to simulate the QCL active layers, together with our collaborators. Based on this powerful tool, the GaN QCL active layers can be designed with a solid theory predictions.
The MBE system and growth technologies have been optimized for thick layer growth and precise control. Thickness, composition, and doping of QCLs are well calibrated.
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| Strategy for Future Research Activity |
First, fabricate the grown QCL structures into real devices. This will be soon conducted. Then the performance of the QCL devices will be measured by J-V and Light output experiments. Based on the first round results, the DMW processing must be optimized to improve the performance.
Another aspect is to precisely determine the transition energy of the intersubband transitions, since it strongly depends on the polarization field in GaN/AlGaN heterostructures. For this purpose, the absorption spectrum is necessary to check polarization charge density, which shows large uncertainty.
The most successful 3 well design scheme for GaAs based QCL is used. However, for GaN based QCLs, 2 well and 4 well design are perhaps should be considered since the leakage problem could be more serious than GaAs.
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