Browsing by Author "Wang, Hsing-Yeh"

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Strain study of self-assembled InAs quantum dots by ion channeling technique
(2006-11-15)
Wang, Hsing-Yeh
;
Lee, Chien-Ping
;
Niu, H.
;
Chen, C. H.
;
Wu, S. -C.
Ion channeling technique using MeV C++ ions was used to study strain in self-assembled InAs quantum dots (QDs) buried in GaAs matrix. Because of the use of heavy ions, we were able to observe an angular shift in the angular scan of the In signal relative to that of the Ga/As signal. This provided a direct evidence that the InAs lattice is larger than that of GaAs in the growth direction. Combining the channeling results in [100] and [110] directions and the photoluminescence emission spectrum, we conclude that the InAs QDs are under tensile strain in the growth direction and have the same lattice constant as that of GaAs in the lateral direction. Thermal annealing causes the strain to relax, first in the growth direction and then in the lateral direction as the annealing temperature increases. The photoluminescence spectra of the QDs before and after annealing indicate, however, that composition intermixing also takes place during annealing and is the dominant factor in determining the band gap energy of the QDs. (c) 2006 American Institute of Physics.
Wavelength switching transition in quantum dot lasers
(2007-02-19)
Wang, Hsing-Yeh
;
Cheng, Hsu-Chieh
;
Lin, Sheng-Di
;
Lee, Chien-Ping
;
電子工程學系及電子研究所
Control and the selection of the ground state emission and/or the excited state emission of an InAs quantum dot laser have been demonstrated. By controlling the currents injected into each section of a two-section cavity, switching between the ground state emission and the excited state emission with a separation of 100 nm was achieved. With a constant total current, either ground state lasing (similar to 1.3 mu m), excited state lasing (similar to 1.2 mu m), or dual state lasing can be obtained simply by adjusting the current ratio between the two sections. (c) 2007 American Institute of Physics.