| Summary: | 碩士 === 國立交通大學 === 分子科學研究所 === 95 === I have investigated the carrier capture and relaxation processes in InAs/GaAs self-assembled quantum dots at room temperature by time-resolved photo- luminescence techniques previously. So a polarization-resolved photo-luminescence up-conversion spectroscopy was set up from the original time-resolved system. Then we can use it to study carrier spin capture and relaxation in quantum dots, wetting layers, and barrier. The electron and hole spin lifetimes are found (electrons spin: ~100ps; hole spin: ~20ps) at 77K. The rapid relaxation of hole spin is about 100fs in bulk GaAs at room temperature, but it is preserved in quantum dots longer time.
Because up-conversion system is performed with high time resolution, we can do experiments to study carrier spin dynamics in InAs/GaAs quantum dots. The time-resolved measurements reveal that spin relaxation time can not be fit with monoexponential but can be fit with biexponential. The fast decay time is primarily attributed to the carrier-carrier scattering by coulomb interaction. And the slow decay time corresponds to the spin flip process with phonons.
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