2005 Fiscal Year Final Research Report Summary
Optical Control And Application Of Spin Generation And Relaxation
| Project/Area Number |
14076217
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Science and Engineering
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| Research Institution | Waseda University |
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Principal Investigator |
TACKEUCHI Atsushi Waseda University, School of Science And Engineering, Professor, 理工学部, 教授 (80298140)
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| Project Period (FY) |
2002 – 2005
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| Keywords | spin optical control / semiconductor / quantum well / relaxation / 緩和 |
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| Research Abstract |
The exciton spin relaxation mechanism was investigated between 13 and 300 K in InGaAs/InP quantum wells using time-resolved spin-dependent pump and probe absorption measurements. The clear carrier density dependence of the exciton spin relaxation time was observed below 40 K, although the carrier density dependence is weak above 40 K. These results imply that the main spin relaxation mechanism above and below 40 K are the D'yakonov-Perel' process and the Bir-Aronov-Pikus process, respectively.
Carrier spin dynamics was investigated in highly uniform self-assembled InAs quantum dots. The measured spin relaxation time decreases rapidly from 1.1 ns at 10 K to 200 ps at 130 K. This large change in the spin relaxation time is well explained in terms of the mechanism of acoustic phonon emission.
The spin relaxation process of A-band exciton in GaN is observed with sub-picosecond's time resolution. The spin relaxation times at 150-225 K are 0.47-0.25 ps. These are at least one order of magnitude shorter than those of the other III-V compound semiconductors. The excitonic spin relaxation process in cubic GaN is observed. The spin relaxation times at 15 K -75 K are found to be longer than 5 ns. Although these long spin relaxation times are in striking contrast to the sub-picosecond spin relaxation of A-band free excitons in hexagonal GaN, they are consistent with the dependence that spin relaxation time becomes longer for wider-band-gap zincblende semiconductors.
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