Browsing by Author "Chen, T. T."

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Optical properties of InGaN quantum dots grown by SiN(x) nanomasks
(2007-04-15)
Huang, L. L.
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Chang, H. J.
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Chou, Y. Y.
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Wang, C. H.
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Chen, T. T.
InGaN quantum dots (QDs) deposited on SiN(x) nanomasks have been investigated by atomic force microscopy, photoluminescence (PL), and photoluminescence excitation (PLE) measurements. It was found that the size of QDs can be well controlled by SiN(x) nanomasks, enabling the manipulation of quantum confinement effect. The PL spectra of InGaN QDs contain several fine structures, and the main peaks can be attributed to families of QDs with different sizes. The emission arising from InGaN QDs and GaN buffer layer can be clearly distinguished based on PLE measurement, which can be used to improve the interpretation in the previous reports. Our study indicates that the quantum confined Stark effect due to piezoelectric field plays a very important role in the optical properties of InGaN QDs, which is very useful for the application of optoelectronic devices.(c) 2007 American Institute of Physics.
Optically modulated internal strain in InGaN quantum dots grown on SiNx nano masks
(2008-01-21)
Chang, H. J.
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Chen, T. T.
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Huang, L. L.
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Chen, Y. F.
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Tsai, J. Y.
Optically modulated internal strain has been observed in InGaN quantum dots (QDs) deposited on SiNx nano masks. The modulated internal strain can induce a number of intriguing effects, including the change of refractive index and the redshift of InGaN A(1)(LO) phonon. The underlying mechanism can be well accounted for in terms of the variation of internal strain through the converse piezoelectric effect arising from the screening of the internal electric field due to spatial separation of photoexcited electrons and holes. Our results point out a convenient way for the fine tuning of physical properties in nitride-based semiconductor nanostructures, which is very important for high quality optoelectronic devices. (c) 2006 Optical Society of America.
Wire-like characteristics in stacked InAs/GaAs quantum dot superlattices for optoelectronic devices
(2007-09-01)
Chen, T. T.
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Chen, Y. F.
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Wang, J. S.
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Huang, Y. S.
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Hsiao, R. S.
The wire-like characteristics of stacked InAs/GaAs quantum dot (QDs) superlattices induced by the vertically electronic coupling effect were demonstrated by surface photovoltaic and photoluminescence measurements. It was found that the surface photovoltaic signal can be enhanced by up to more than 100 times due to the wire-like behavior along the growth direction. We also found that the emission from the cleaved edge surface is strongly anisotropic, which suggests a possibility of fine tuning the polarization by changing the spacer thickness. Additionally, the electroluminescence of stacked QDs near 1.3 mu m based on the wire-like characteristics has a much better performance than that of uncoupled QDs.