Browsing by Author "Chung, Pei-Kang"

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Analysis of two-phonon infrared spectral features of gallium arsenide and indium phosphide by first-principles calculations
(2014-12)
Lin, Huang-Hsiang
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Chung, Pei-Kang
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Yen, Shun-Tung
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電機學院
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電子工程學系及電子研究所
We perform a self-consistent calculation based on density functional perturbation theory to analyze the infrared spectral features of GaAs and InP arising from two-phonon processes. The features are identified and assigned the critical points in the first Brillouin zone. Distribution of the critical points is investigated. The analysis demonstrates that collections of phonons of wave vectors around symmetry points and along symmetry lines are responsible for strong infrared features in two-phonon processes.
Efficient far-infrared thermal bremsstrahlung radiation from a heterojunction bipolar transistor
(2015-08-28)
Chung, Pei-Kang
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Yen, Shun-Tung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We investigate the far-infrared thermal radiation properties of a heterojunction bipolar transistor. The device conveniently provides a high electric field for electrons to heat the lattice and the electron gas in a background with ions embedded. Because of very high effective temperature of the electron gas in the collector, the electron-ion bremsstrahlung makes efficient the thermal radiation in the far-infrared region. The transistor can yield a radiation power of 0.1 mW with the spectral region between 2 and 75 THz and a power conversion efficiency of 6 x 10(-4). Such output contains a power of 20 mu W in the low-frequency part (2-20 THz) of the spectrum. (C) 2015 AIP Publishing LLC.
Enhanced thermal radiation in terahertz and far-infrared regime by hot phonon excitation in a field effect transistor
(2014-11-14)
Chung, Pei-Kang
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Yen, Shun-Tung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We demonstrate the hot phonon effect on thermal radiation in the terahertz and far-infrared regime. A pseudomorphic high electron mobility transistor is used for efficiently exciting hot phonons. Boosting the hot phonon population can enhance the efficiency of thermal radiation. The transistor can yield at least a radiation power of 13 mu W and a power conversion efficiency higher than a resistor by more than 20%. (C) 2014 AIP Publishing LLC.
Extraction of infrared optical constants from fringing reflectance spectra
(2014-10-21)
Chung, Pei-Kang
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Yen, Shun-Tung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We propose a simple and reliable method for extracting the optical constants of homogeneous dielectrics which can be pure or impure, and polar or nonpolar. The extraction is made from fringing reflectance spectra of slab samples with and without metal on the backside. The method is demonstrated to work well for polar semiconductors GaAs and InP in the infrared regime. The extracted extinction coefficient spectra exhibit plenty of features which correspond well to those in absorption and Raman spectra. (C) 2014 AIP Publishing LLC.
Extraction of optical constants from maxima of fringing reflectance spectra
(2015-02-01)
Yen, Shun-Tung
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Chung, Pei-Kang
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We propose a scheme to extract the refractive index and the extinction coefficient of dielectrics. The extraction needs only a reflectance spectrum with reliable successive maxima of fringing oscillations measured from a dielectric film that is either freestanding or on metal. With the film thickness known in advance, we determine the refractive index spectrum from the fringing oscillation periods and then the extinction coefficient spectrum from the upper envelope. The method is demonstrated to work well for GaAs and Ge. (C) 2015 Optical Society of America
Far-infrared quasi-monochromatic perfect absorption in a thin GaAs film on gold
(2015-08-15)
Yen, Shun-Tung
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Chung, Pei-Kang
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We study the far-infrared absorption properties of a thin GaAs film on Au. We show that a 1.2-mu m GaAs film on Au can completely absorb an electromagnetic wave of 7.9 THz and totally reflect the waves of frequencies not very close to 7.9 THz. The uniformity of the layered structure enables observation of a quasi-monochromatic, nearly perfect absorption of 96% in a 1.4-mu m GaAs film. The absorption can be high for a wide range of incident angles. (C) 2015 Optical Society of America
Optical properties and potential applications of epsilon-GaSe at terahertz frequencies
(2009-09-01)
Chen, Ching-Wei
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Tang, Tsung-Ta
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Lin, Sung-Hui
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Huang, Jung Y.
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Chang, Chen-Shiung
Ordinary and extraordinary refractive indices of an epsilon-GaSe crystal at terahertz (THz) frequencies are experimentally determined in this study. Fitting experimental data by THz time-domain spectroscopy (THz-TDS) and a Fourier transform infrared spectrometer (FTIR), we proposed revised complex dielectric functions and Sellmeier equations of GaSe for both ordinary and extraordinary waves from 0.2 to 100 THz. Phonon vibrational modes and overtones in the THz frequency range are examined in detail. The high magnitude of the figure of merit (FOM similar to 10(3) at 1 THz), the large birefringence (Delta n similar to 0.76 at 1 THz). and the low absorption coefficient (alpha similar to 0.2 cm(-1) at 1 THz) of GaSe are also identified. Potential applications to practical photonic devices such as phase shifters at THz frequencies are proposed. (C) 2009 Optical Society of America