Browsing by Author "Chuang, C. -H."

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Free carrier dynamics of InN nanorods investigated by time-resolved terahertz spectroscopy
(2009-01-15)
Ahn, H.
;
Chuang, C. -H.
;
Ku, Y. -P.
;
Pan, C. -L.
;
光電工程學系
Ultrafast time-resolved terahertz spectroscopy is employed to investigate the carrier dynamics of indium nitride (InN) nanorod arrays and an epitaxial film. Transient differential transmission of terahertz wave shows that hot carrier cooling and defect-related nonradiative recombination are the common carrier relaxation processes for InN film and nanorods. However, the electrons confined in the narrow structure of nanorods are significantly affected by the carrier diffusion process near the surface, which causes the abnormally long relaxation time for nanorods.
Grain-size-related transient terahertz mobility of femtosecond-laser-annealed polycrystalline silicon
(2009-09-01)
Wang, Y. -C.
;
Ahn, H.
;
Chuang, C. -H.
;
Ku, Y. -P.
;
Pan, C. -L.
We investigated carrier-relaxation dynamics of femtosecond laser annealed (FLA) polycrystalline silicon (poly-Si). The correlation between morphology and electrical properties of poly-Si after femtosecond laser annealing is elucidated by optical-pump-terahertz-probe and terahertz time-domain spectroscopies. The transient conductivities of FLA-processed poly-Si with large (similar to 500 nm) and small (similar to 50 nm) grain sizes were both well fitted by the Drude model in the terahertz regime from 0.4 to 2 THz. The transient mobilities of these materials were determined to be 175 +/- 19.4 and 94.5 +/- 20.2 cm(2)/V s, respectively. After annealing, reduction of deep-state density rather than tail-state density in large-grain poly-Si is responsible for its higher mobility.
Intense terahertz emission from a-plane InN surface
(2008-03-10)
Ahn, H.
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Ku, Y. -P.
;
Chuang, C. -H.
;
Pan, C. -L.
;
Lin, H. -W.
We report a significant enhancement in terahertz emission from the indium nitride (InN) films grown along the a axis (a-plane InN), relative to the InN films grown along the c axis. The primary radiation mechanism of the a-plane InN film is found to be due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field perpendicular to the a axis, which effectively enhances the geometrical coupling of the radiation out of semiconductor. In addition, azimuthal angle dependence measurement shows that the p-polarized terahertz output consists of a large angularly independent component and a weak component with a distinctive fourfold rotation symmetry. (c) 2008 American Institute of Physics.
Terahertz spectroscopic study of vertically-aligned InN nanorods (vol 91, 163105, 2007)
(2009-05-04)
Ahn, H.
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Ku, Y. -P.
;
Wang, Y. -C.
;
Chuang, C. -H.
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Gwo, S.