Browsing by Author "Jang, DJ"

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Carrier capture and relaxation of self-assembled ZnTe/ZnSe quantum dots prepared under Volmer-Weber and Stranski-Krastanow growth modes
(2005-02-01)
Lee, ME
;
Yeh, YC
;
Chung, YH
;
Wu, CL
;
Yang, CS
The carrier capture and relaxation of type II ZnTe/ZnSe quantum dots have been investigated with ultrafast time-resolved photo luminescence upconversion. The carrier capture times were 7 and 38 ps for the Volmer-Weber mode and Stranski-Krastanow mode, respectively. We found that the carrier relaxation of QDs exhibits faster decay under the Volmer-Weber growth mode than under the Stranski-Krastanow growth mode. We attribute the difference of carrier relaxation to the wetting layer formed in the Stranski-Krastanow growth mode. (C) 2004 Elsevier B.V. All rights reserved.
Optical properties of self-assembled ZnTe quantum dots grown by molecular-beam epitaxy
(2005-02-01)
Yang, CS
;
Lai, YJ
;
Chou, WC
;
Chen, WK
;
Lee, MC
The morphology and the size-dependent photoluminescence (PL) spectra of the type-II ZnTe quantum dots (QDs) grown in a ZnSe matrix were obtained. The coverage of ZnTe varied from 2.5 to 3.5 monolayers (MLs). The PL peak energy decreased as the dot size increased. Excitation power and temperature-dependent PL spectra are used to characterize the optical properties of the ZnTe quantum dots. For 2.5- and 3.0-ML samples, the PL peak energy decreased monotonically as the temperature increased. However, for the 3.5-ML sample, the PL peak energy was initially blueshifted and then redshifted as the temperature increased above 40 K. Carrier thermalization and carrier transfer between QDs are used to explain the experimental data. A model of temperature-dependent linewidth broadening is employed to fit the high-temperature data. The activation energy, which was found by the simple PL intensity quenching model, of the 2.5, 3.0, and 3.5 MLs were determined to be 6.35, 9.40, and 18.87 meV, respectively. (C) 2005 American Institute of Physics.