| 研究実績の概要 |
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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