| 研究実績の概要 |
Research has progressed in the last year. Samples of GaN/AlGaN quantum wells with various Zinc dopant densities have been grown and characterized optically using micro photoluminescence under both pulsed and continuous wave excitation at various wavelengths. The Zinc dopants are optically active, (as was expected), at blue emission wavelengths from 400nm~480nm. Importantly, sharp emission peaks have been observed for lower Zinc density samples, indicating that isolated centers (or at least a low number of emitters with the same energy) are being probed. The emission linewidths of the peaks range from 2meV to 7meV, and the emission lifetimes are ~1.5ns - 2ns. To the best of our knowledge this is the first time such peaks have been observed from Zinc doped GaN materials. Initial measurements on the spectral diffusion (an important topic in III-nitride materials due to large internal piezoelectric and pyroelectric fields) have also been carried out, revealing that the emission is quite stable, with peak energy variations of much less than 0.2meV (less than 1/10 of the peak linewidth). Unfortunately, single photon has not yet been observed, and this is the topic that will now be pursued in earnest in the second year with the current samples.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
As planned, several samples have been fabricated and analysis is progressing smoothly. The plan of this project is to observe single photon emission from Zinc related states in III-nitride semiconductors, and although single photon emission has (unfortunately) not been realized yet, several key aspects of the emission properties have indeed been understood. For example, it has been elucidated that emission is observed under excitation into the GaN quantum well- indicating that the excited carriers diffuse and become captured by the the Zinc traps (rather than by some form of direct excitation or optical injection). It has also been verified (via time resolved micro photoluminescence studies using a femtosecond pulsed excitation) that the emission lifetimes of the states are of order 1.5ns-2ns - meaning that any single photon emission from these states will, in principle, be temporarily resolvable by the available microphotoluminescence system (using either pulsed or CW emission). This information is important because it will allow for more excitation conditions to be tried for the eventual realization of single photon emission from these emitters.
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| 今後の研究の推進方策 |
In the next year experiments will be performed to continue to try to realize and observe single photon emission from the Zinc related states. This will include
1) Continued sample mapping and characterization to observe appropriate peaks due to localized emission centers.
2) Possible sample modification (via the formation of etched mesas) to further reduce the density of measured emission centers at any one time.
Additionally, standard microphotoluminescence measurements will also be carried out to fully characterize the Zinc related states. In the event that single photon emission can not be realized, this information will be disseminated to the research community via a publication and conference presentation.
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