Browsing by Author "Jian, S. R."

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Carrier Dynamics in Self-Assembled CdTe Stranski-Krastanow Quantum Dots Grown on ZnSe by Molecular Beam Epitaxy
(2008-11-01)
Yang, C. S.
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Chin, K. F.
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Lai, J. Y.
;
Luo, C. W.
;
Chou, W. C.
Self-assembled CdTe/ZnSe Stranski-Krastanow quantum-dot (QD) structures, which have a CdSe-like precursor-layer (PCL) between CdTe quantum dots and ZnSe matrix, were grown by molecular beam epitaxy. The carrier dynamics of the structures was studied by photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements. The temperature-dependent PL spectra revealed that there is a carrier transformation from small dots to larger dots via the precursor layer. Temperature-dependent PL measurements verify the existence of the QD excited excitonic state in 5.0 mono-layer (ML) coverage. In 0.6 ML coverage, the TRPL spectra exhibited a double-exponential decay process, as the detection energy at PCL emission energy. The faster decay time is corresponded to the carrier lifetime in PCL, the slower decay time exhibits the carrier in small QD. However, in 5.0 ML coverage, a faster and slower decay time represents the carrier lifetime in QD excited state for larger QD and the carrier lifetime in QD ground state for smaller QD.
Electric-field-controlled electron relaxation in lateral double quantum dots embedded in a suspended slab
(2008-11-15)
Liao, Y. Y.
;
Chuu, D. S.
;
Jian, S. R.
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電子物理學系
;
Department of Electrophysics
This study investigates phonon-induced electron relaxation in a lateral double quantum dot that is embedded in a suspended slab. Exact calculations are made in electric fields. The dependence of the relaxation rate on the parameters of the dots and the slabs is analyzed. Numerical results indicate that the relaxation rate depends strongly on the phonon character of the slab. Unlike in the bulk environment, phonon-subband quantization clearly influences the behavior. In particular, the relaxation rate can be greatly suppressed or enhanced by tuning the electric fields. This fact may be useful in manipulating the relaxation rate in lateral double quantum dots.
Formation of a precursor layer in self-assembled CdTe quantum dots grown on ZnSe by molecular beam epitaxy
(2007-09-26)
Yang, C. S.
;
Wang, J. S.
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Lai, Y. J.
;
Luo, C. W.
;
Chen, D. S.
The growth mode of CdTe quantum dots ( QDs) grown on highly lattice-mismatched ZnSe buffer was investigated. CdTe QDs ( 0.6 to 5.0 mono-layers ( MLs)) were deposited on the Se-stabilized ZnSe buffer layers using an alternating supply of Cd and Te atomic sources. Cross-sectional transmission electron microscopy and photoluminescence ( PL) measurements revealed the existence of a CdSe-like two-dimensional precursor layer ( PCL). The prominent difference in the temperature-dependent PL peak shift was associated with the emissions from the respective CdSe PCL and CdTe QDs. In addition, the PL excitation measurement demonstrated the existence of the first QD excited excitonic state.