Browsing by Author "Fu, CP"

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Growth mode transfer of self-assembled CdSe quantum dots grown by molecular beam epitaxy
(2006-01-15)
Lai, YJ
;
Lin, YC
;
Fu, CP
;
Yang, CS
;
Chia, CH
Self-assembled CdSe/ZnSe quantum dots (QDs) were grown at various growth temperatures on GaAs (0 0 1) by molecular beam epitaxy. An optimum growth temperature for CdSe/ZnSe QDs was found to be 260 degrees C. The Stranski-Krastanow (SK) growth mode was confirmed clearly by atomic force microscopy images. The coherent SK QDs were observed from 2.5 monolayers (MLs). Two types of QDs were found with the CdSe coverage of 3.0 MLs. It was attributed to a growth mode change from the coherent SK growth mode to the ripening growth mode. A schematic diagram of the growth mechanism of self-assembled CdSe QDs was presented. Moreover, the photoluminescence spectra of samples with various thicknesses were investigated. A dramatic change of optical properties confirmed that the QD structure formed with thickness above 2.5 MLs. Finally, the dot size and the density distributions were controlled after growth by in-chamber thermal annealing. For the sample grown at 3.0 MLs, the distribution of dot sizes was controlled from 6.0 to 6.5 x 10(3) nm(3) at an annealing temperature of 400 degrees C. (c) 2005 Published by Elsevier B.V.
Optical characterization of ZnSe epilayers and ZnCdSe/ZnSe quantum wells grown on Ge/Ge0.95Si0.05/Ge0.9Si0.1/Si virtual substrates
(2006-03-15)
Ku, JT
;
Kuo, MC
;
Shen, JL
;
Chiu, KC
;
Yang, TH
Several approaches have been employed to grow high-quality ZnSe epilayers on Ge/Ge0.95Si0.05/Ge0.9Si0.1/Si virtual substrates. The ZnSe epilayers were characterized by photoluminescence spectroscopy. Migration enhanced epitaxy and inserting an in situ thermal annealing ZnSe buffer layer effectively reduced the intensity of deep level emissions from the ZnSe epilayer grown on a 6 degrees-tilted Ge/Ge0.95Si0.05/Ge0.9Si0.1/Si virtual substrate. Optimized conditions for growing high-quality ZnSe were used to deposit ZnCdSe/ZnSe multiple quantum wells on Ge/Ge0.95Si0.05/Ge0.9Si0.1/Si virtual substrates. Photoluminescence spectroscopy revealed quantum-confinement effect in the ZnCdSe multiple quantum wells. The evolution of the exciton emission peak energy and the linewidth as a function of temperature indicate a low density of localized sites in the sample with a well width of 1 nm. In the high-temperature regime, the thermal quenching of the excitonic emission intensity from ZnCdSe quantum well structures was governed by the thermal activation of carriers from quantum-well-confined states into barrier states. (c) 2006 American Institute of Physics.