Browsing by Author "Lin, S. D."

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2-3 mu m mid infrared light sources using InGaAs/GaAsSb "W" type quantum wells on InP substrates
(2010-11-15)
Pan, C. H.
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Lin, S. D.
;
Lee, C. P.
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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 have investigated the InGaAs/GaAsSb/InAlGaAs/InAlAs type-II "W" quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The photoluminescence (PL) emission wavelength longer than 2.56 mu m at room temperature (RT) is demonstrated for the first time in this material system. The PL emission peaks of our designed samples can cover a wide range from 2 to 2.5 mu m at cryogenic temperature. The samples show good optical quality that the reduction in integrated PL intensity is only around one order of magnitude from 35 K to RT. We found that the integrated PL intensity decreased as the emission wavelength increased, which is due to the reduction in the electron-hole wave function overlap. This is consistent with the calculated result. In the power dependent PL measurements, the emission peak of "W" type QWs show blue shifts with the excitation power (P-ex) but does not follow the P-ex(1/3) rule as predicted by type-II band bending model. The localized states filling effect gives reasonable explanations for the observed phenomena. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506427]
2-3 mu m mid infrared light sources using InGaAs/GaAsSb "W" type quantum wells on InP substrates
(2010-11-15)
Pan, C. H.
;
Lin, S. D.
;
Lee, C. P.
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have investigated the InGaAs/GaAsSb/InAlGaAs/InAlAs type-II "W" quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The photoluminescence (PL) emission wavelength longer than 2.56 mu m at room temperature (RT) is demonstrated for the first time in this material system. The PL emission peaks of our designed samples can cover a wide range from 2 to 2.5 mu m at cryogenic temperature. The samples show good optical quality that the reduction in integrated PL intensity is only around one order of magnitude from 35 K to RT. We found that the integrated PL intensity decreased as the emission wavelength increased, which is due to the reduction in the electron-hole wave function overlap. This is consistent with the calculated result. In the power dependent PL measurements, the emission peak of "W" type QWs show blue shifts with the excitation power (P(ex)) but does not follow the P(ex)(1/3) rule as predicted by type-II band bending model. The localized states filling effect gives reasonable explanations for the observed phenomena. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506427]
A simple method to characterize the afterpulsing effect in single photon avalanche photodiode
(2008-09-01)
Yen, H. T.
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Lin, S. D.
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Tsai, C. M.
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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
A simple method is introduced for studying the afterpulsing effect in InGaAs single photon avalanche photodiode. The afterpulsing probability is obtained through measuring the detection efficiencies of various biasing pulses, while the incident photons are kept constant. The effect of excess bias and temperature on the afterpulsing probability is investigated. When the device temperature is higher than 170 K, the afterpulsing probability is lower than 5% for all excess bias voltages because the trapped carrier lifetime is much shorter than the repetition period. (C) 2008 American Institute of Physics.
Anomalous diamagnetic shift for negative trions in single semiconductor quantum dots
(2010-03-01)
Fu, Y. J.
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Lin, S. D.
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Tsai, M. F.
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Lin, H.
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Lin, C. H.
We report on the magnetic response of negative trions X(-) in single self-assembled InAs/GaAs quantum dots. Unlike the conventional quadratic diamagnetic shift for neutral excitons, the observed X(-) diamagnetic shifts are small and nonquadratic. In particular, we also observed a reversal in sign of the conventional diamagnetic shift. A theoretical analysis indicates that such anomalous behaviors for X(-) arise from an apparent change in the electron wave function extent after photon emission due to the strong Coulomb attraction induced by the hole in its initial state. This effect can be very pronounced in small quantum dots, where the electron wave function becomes weakly confined and extended much into the barrier region. When the electrons gradually lose confinement, the magnetic response of X(-) will transit gradually from the usual quadratic diamagnetic shift to a quartic dependence, and finally into a special paramagnetic regime with an overall negative energy shift.
Carrier Dynamics in InAs/GaAs Quantum Rings
(2009)
Lin, C. H.
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Ling, H. S.
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Sun, K. W.
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Lee, C. P.
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Lin, S. D.
We have investigated the temperature dependence of the carrier relaxation dynamics in InAs/GaAs self-assembled quantum rings by using the time-resolved photoluminescence technique with a time resolution of similar to 250 ps. The carrier relaxation in the QRs not only shows strong dependence on the lattice temperature, it is also significant slower than the carrier relaxation in the quantum dots at temperature above 150 K.
Effect of the electromagnetic environment on the dynamics of charge and phase particles in one-dimensional arrays of small Josephson junctions
(2011-11-01)
Ho, I. L.
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Kuo, W.
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Lin, S. D.
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Lee, C. P.
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Liang, C. T.
The effect of the electromagnetic environment on the dynamics of quasi-particles, Cooper pairs and phase particles in one-dimensional arrays of small Josephson junctions is investigated experimentally and theoretically. It is found that the environment enhances the phase ordering and thus suppresses quasi-particle tunneling at high temperature and localization of Cooper pairs at low temperature. The dynamics is studied in the context of phase-charge duality, and the experimental results are quantitatively analyzed in both charge-ordered and phase-ordered regimes. Based on these analyses, a low-temperature phase diagram as well as a finite-temperature crossover phase diagram are constructed and compared to the experimental diagrams. Copyright (C) EPLA, 2011
Electron delocalization of tensily strained GaAs quantum dots in GaSb matrix
(2010-12-15)
Lin, T. C.
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Wu, Y. H.
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Li, L. C.
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Sung, Y. T.
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Lin, S. D.
The magneto-optical response of type-II tensily strained GaAs self-assembled quantum dots in GaSb was investigated in magnetic fields up to 14 T. By depositing different GaAs amount, the dot sizes and the corresponding emission energies were varied. We analyzed the carrier wave function extent of different dots using the diamagnetic shift results. It was found that, with the increase in the energy (the reduction in the dot size), the diamagnetic coefficient first rises quickly and then saturates at around 21 mu eV/T(2). Based on a simple calculation model, this unusual tendency is attributed to the electrons gradually spilling out of the quantum dot to the wetting layer as the dots get smaller. This delocalization effect is enhanced in this material system due to the tensile strain relaxation within the dots, which raises the conduction band edge over that in the wetting layer. (c) 2010 American Institute of Physics. [doi: 10.1063/1.3520669]
"Embedded Emitters": Direct bandgap Ge nanodots within SiO2
(2016-12-21)
Kuo, M. H.
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Chou, S. K.
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Pan, Y. W.
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Lin, S. D.
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George, T.
Microdisk-arrays of vertically stacked 30-70nm Ge nanodots embedded within SiO2 were fabricated using thermal oxidation of Si0.75Ge0.25 abacus-shaped pillars and followed by post-annealing in oxygen-deficient conditions. The Ge nanodots are subjected to increasing quantum-confinement and tensile-strain by reducing dot size. We show that considerable quantum-confinement and tensile-strain can be generated within 30 nm Ge nanodots embedded in SiO2, as evidenced by large Raman red shifts for the Ge-Ge phonon lines in comparison to that for bulk Ge. These large quantum-confinement and tensile-strain facilitate direct-bandgap photoluminescence experimentally observed for the Ge nanodots, and are consistent with the strain-split photoluminescence transitions to the light-hole (LH) and heavy-hole (HH) valence bands at 0.83 eV and 0.88 eV, respectively. Time-resolved photoluminescence measurements conducted from 10-100K show temperature-insensitive carrier lifetimes of 2.7 ns and 5 ns for the HH and LH valence-band transitions, respectively, providing additional strong evidence of direct bandgap photoluminescence for tensile-strained Ge nanodots. Published by AIP Publishing.
Frequency dependence of negative differential capacitance in Schottky diodes with InAs quantum dots
(2008-09-08)
Lin, S. D.
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Ilchenko, V. V.
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Marin, V. V.
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Panarin, K. Y.
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Buyanin, A. A.
The frequency dependence of negative differential capacitance (NDC) in Schottky diodes with InAs quantum dots (QDs) is studied. The measured peak capacitances of NDC decay rapidly as the testing frequencies are higher than a few kilohertz. A kinetic model considering the testing signal is proposed and the capture rates of QDs are extracted. The simulation result is quantitatively consistent with the experimental data when the charging effect in QDs is included. (c) 2008 American Institute of Physics.
Observation of the negative differential capacitance in Schottky diodes with InAs quantum dots near room temperature
(2007-06-25)
Lin, S. D.
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Ilchenko, V. V.
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Marin, V. V.
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Shkil, N. V.
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Buyanin, A. A.
The negative differential capacitance (NDC) of Schottky diodes with the layers of InAs quantum dots (QDs) has been clearly observed near room temperature. A simple model involving two zero-dimensional quantum states is proposed to explain the NDC behavior. The simulation results show that the NDC is caused by the fast charging-discharging process in the second states of QDs.
Optical fine structures of highly quantized InGaAs/GaAs self-assembled quantum dots
(2010-06-30)
Ramirez, H. Y.
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Lin, C. H.
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Chao, C. C.
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Hsu, Y.
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You, W. T.
A theoretical model for the electron-hole exchange interaction in three-dimensionally (3D) confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings (FSSs) of small InGaAs/GaAs self-assembled quantum dots (QDs) with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged e-h exchange interaction and leads to the reduced FSSs in the regime of high emission energy.
Ordering of stacked InAs/GaAs quantum-wires in InAlAs/InGaAs matrix on (100) InP substrates
(2008-01-01)
Lin, Z. C.
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Lin, S. D.
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Lee, C. P.
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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
Stacked and wire-like InAs/GaAs nanostructures in InGaAs/InAlAs matrix on InP substrates were grown by molecular beam epitaxy (M BE) and investigated by atomic force microscope (AFM) and transmission electron microscope (TEM). Cross-sectional TEM images showed that the stacked InAs and GaAs quantum-wires in InGaAs matrix were vertically aligned to form a rectangular lattice. In contrast, in InAlAs matrix, the stacked InAs quantum-wires were cross-correlated to form a bcc like lattice. Clear composition modulation was observed in the post-grown matrix material. Based on this result, a kinetic growth model is proposed to explain the stacking behavior of the quantum-wires. (C) 2007 Elsevier B.V. All rights reserved.
Probing mobility gaps at resistivity minima in the integer quantum Hall effect
(2008)
Liang, C. -T.
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Chen, K. Y.
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Wu, Jau-Yang
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Lin, S. D.
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Lin, Li-Hung
Magneto-transport measurements are performed on the AlGaAs/GaAs quantum Hall (QH) devices fabricated recently by our group. A series of Hall plateaus are observed with increasing the perpendicular magnetic field, and the mobility gaps resulting from localization effects are investigated at the minima in the longitudinal resistivity. Only the gap corresponding to the filling factor i=2 is close to the expected cyclotron energy, and our study supports that the low-field QH conductors may suffer problems due to insufficient localization. The anomalous change on the Hall slope is observed when the i=3 plateau is destroyed by the large current.
Room temperature negative differential capacitance in self-assembled quantum dots
(2008-12-07)
Ilchenko, V. V.
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Marin, V. V.
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Lin, S. D.
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Panarin, K. Y.
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Buyanin, A. A.
The negative differential capacitance (NDC) of Schottky diodes with layers of InAs quantum dots (QDs) has been clearly observed at room temperature. The frequency dependence of the NDC is investigated. The measured peak capacitances of NDC decay rapidly at the testing frequencies higher than a few kilohertz. A kinetic model considering the testing signal is proposed and the capture rates of QDs are extracted. The simulation result is quantitatively consistent with the experimental data when the charging effect in QDs is included.
Shape dependent carrier dynamics in InAs/GaAs nanostructures
(2009-12-01)
Lin, C. H.
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Ling, H. S.
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Su, S. K.
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Lin, S. D.
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Lee, C. P.
We present systematic experimental studies of the temperature dependence of continuous wave and time-resolved photoluminescence spectroscopy in self-assembled InAs/GaAs nanostructures as the shape of quantum structures evolved from dot to ring. The carrier dynamics show strong dependence on the geometrical shape of the nanostructures under investigation. An increase in photoluminescence decay time of the excited and ground states is observed as the shape of nanostructures changed from dot, volcano, to ring. It is attributed to the carrier thermalization between the dark and ground states. The photoluminescence excitation spectra of the quantum rings reveal resonances related to the dark states. A rate equation model is proposed to interpret the observed carrier dynamics.
Single-photon avalanche diodes in 0.18-mu m high-voltage CMOS technology
(2017-06-12)
Huang, L. D.
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Wu, J. Y.
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Wang, J. P.
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Tsai, C. M.
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Huang, Y. H.
We have designed and fabricated high-performance single-photon avalanche diodes (SPADs) by using 0.18-mu m high-voltage CMOS technology. Without any technology customization. the SPADs have low dark-count rate, high photon-detection probability, low afterpulsing probability, and acceptable timing jitter and breakdown voltage. Our design provides a low-cost and high-performance SPAD for various applications. (C) 2017 Optical Society of America
Superconductivity in an Aluminum Film Grown by Molecular Beam Epitaxy
(2012-08-01)
Liang, C. -T.
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Yeh, M. -R.
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Lin, S. D.
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Lin, S. W.
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Wu, J. Y.
We report on superconductivity in an aluminum film grown on a GaAs substrate by molecular beam epitaxy (MBE). We show that the quality of the MBE-grown sample is better than that of its counterpart prepared by electron gun evaporation. This is evidenced by the observed much lower resistivity, higher critical current, longer coherence length, and downward critical field-temperature characteristic H-c(T). Our results suggest that a MBE-grown Al thin film can be used to study superconductivity in a relatively clean metal.
Temperature dependence of time-resolved photoluminescence spectroscopy in InAs/GaAs quantum ring
(2009-05-04)
Lin, C. H.
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Lin, H. S.
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Huang, C. C.
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Su, S. K.
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Lin, S. D.
We present detailed experimental results of the temperature dependence of continuous wave and time-resolved photoluminescence (PL) spectroscopy in self-assembled InAs/GaAs quantum dot and quantum ring nanostructures. A dramatic increase in PL decay time of the excited and ground states is observed in InAs quantum rings at high temperature. We speculate that the longer PL lifetime in quantum rings is due to the interplay among the dark states, ground states, and the reduced wave function overlapping between electrons and holes. A rate equation model is proposed to interpret the observed temperature dependence of the ground state exciton lifetime.
Transmission electron microscopy studies of GaAs nanostructures in InGaAs/InP matrix grown by molecular beam epitaxy
(2006-09-01)
Lin, S. D.
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Lin, Z. C.
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Lee, C. P.
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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
Self-assembled GaAs nanostructures in In0.53Ga0.47As matrix on (100) InP substrate have been investigated using atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM). In measured AFM images, dotlike and wirelike GaAs nanostructures were obtained with different deposition thicknesses. The XTEM images clearly showed composition modulation in the overgrown InGaAs matrix. The reason for this composition modulation is explained by strain field compensation and surface energy minimization. (c) 2006 American Institute of Physics.
Wide spectral range confocal microscope based on endlessly single-mode fiber
(2010-08-30)
Hubbard, R.
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Ovchinnikov, Yu. B.
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Hayes, J.
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Richardson, D. J.
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Fu, Y. J.
We report an endlessly single mode, fiber-optic confocal microscope, based on a large mode area photonic crystal fiber. The microscope confines a very broad spectral range of excitation and emission wavelengths to a single spatial mode in the fiber. Single-mode operation over an optical octave is feasible. At a magnification of 10 and lambda = 900 nm, its resolution was measured to be 1.0 mu m (lateral) and 2.5 mu m (axial). The microscope's use is demonstrated by imaging single photons emitted by individual InAs quantum dots in a pillar microcavity. (C) 2010 Optical Society of America