2019 Fiscal Year Research-status Report
Efficient Single Photon Emission From III-Nitride Quantum Dots
| Project/Area Number |
19K15039
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Holmes Mark 東京大学, 生産技術研究所, 准教授 (90760570)
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| Project Period (FY) |
2019-04-01 – 2021-03-31
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| Keywords | III-nitride / quantum dot |
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| Outline of Annual Research Achievements |
In order to increase the photon extraction efficiency from III-nitride quantum dots, and allow for the development of more efficient single photon emitters, the design of a bullseye structure was performed for GaN/AlN quantum dots, and device fabrication was optimized and performed using e-beam lithography and reactive ion etching. For initial experiments a device structure consisting of 5 concentric annular trenches etched around a central nanowire structure was used. Such a device suppresses lateral photon emission from the QDs, and enhances the emission rate into the out-of-plane direction so that the photons can be more efficiently captured using an objective lens. Etching was performed into a sample of self-assembled GaN quantum dots that emit in the wavelength region of ~310nm. Optical characterization of processed devices revealed that, although fabrication was imperfect, a clear improvement of the photon extraction efficiency from the quantum dots could be realized. Statistical data was measured from several devices (>100), and the average enhancement ratio was measured to be ~6.9 (into a lens with a numerical aperture of 0.4), relative to quantum dots in unprocessed areas of the sample. In some cases sharp emission peaks could be observed, which are promising signs for the isolation of emission from individual quantum dots.
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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
Devices have been designed and successfully fabricated. The fabricated devices clearly exhibit an increase in the photon extraction efficiency (which has been confirmed from testing a large number of devices). Further simulation work has shown that (using somewhat unrealistic device design involving an underlying mirror) extraction efficiencies exceeding 90% may be achievable for lenses with numerical apertures of >0.9.
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| Strategy for Future Research Activity |
Work will proceed in two main paths: both experimentally and theoretically. This will include the experimental spectral isolation of a single quantum dot within a structure such that single photons can be extracted with high efficiency. Further design of the devices (with different spatial geometry and annular frequency) will also be performed to test if enhanced emission could be achieved with easier device fabrication.
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