M. Hong

National Taiwan University, T’ai-pei, Taipei, Taiwan

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Publications (434)822.8 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Y2O3, as a common high κ gate dielectric, has been directly deposited on (In)GaAs, GaSb, and Ge using electron beam evaporation in ultra-high vacuum. These semiconductors have distinctly different chemical bonding and surface electronic characteristics. No interfacial passivation layer was employed. High-quality Y2O3/semiconductor interfaces have been achieved, resulting in low interfacial trap densities and high-temperature thermal stability, essential for the CMOS compatible process. Self-aligned inversion channel n-InGaAs, p-GaSb, and p-Ge MOSFETs have been fabricated with excellent device performances.
    Microelectronic Engineering 11/2015; 147:330-334. DOI:10.1016/j.mee.2015.04.098 · 1.34 Impact Factor
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    ABSTRACT: Spin pumping effect in Bi2Se3/Fe3Si and Fe/Bi2Te3 heterostructures was studied. High quality films of Bi2Se3(001) on ferromagnetic Fe3Si(111) layer and Fe(111) films on Bi2Te3(001) layer were grown epitaxially by molecular beam epitaxy. Using a microwave cavity source, large voltages due to the Inverse Spin Hall Effect (VISHE) were detected in Bi2Se3(001)/Fe3Si(111) bi-layer at room temperature. VISHE of up to 63.4 ± 4.0 μV at 100 mW microwave power (PMW) was observed. In addition, Fe(111)/Bi2Te3(001) bi-layer also showed a large VISHE of 3.0 ± 0.1 μV at PMW of 25 mW. VISHE of both structures showed microwave linear power dependence in accordance with the theoretical model of spin pumping. The spin Hall angle was calculated to be 0.0053 ± 0.002 in Bi2Se3 and was estimated to be 0.0068 ± 0.003 in Bi2Te3. The charge current density (Jc) of Bi2Se3/Fe3Si and Fe/Bi2Te3 structures are comparable and are about 2-5 times higher than the Fe3Si/normal metal and Fe3Si/GaAs results. The significant enhancement of spin current in topological insulator/ferromagnetic metal (TI/FM) and FM/TI bilayers is attributed to strong spin-orbit coupling inherent of TIs and demonstrates the high potential of exploiting TI-based structures for spintronic applications.
    Journal of Applied Physics 05/2015; 117(17):17D148. DOI:10.1063/1.4918631 · 2.19 Impact Factor
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    ABSTRACT: In situ atomic layer deposited (ALD) Y2O3 films 1-5 nm thick on GaAs(0 0 1)-4 × 6 reconstructed substrates were found to be single crystalline. The epitaxial growth between the oxide films and GaAs was first observed using reflective high energy electron diffraction (RHEED) and later studied using high-resolution synchrotron radiation X-ray diffraction. The Y2O3 films are of cubic phase and have (1 1 0) as the film normal; the orientation relationship between the Y2O3 films and the GaAs substrates was determined to be Y2O3(1 1 0)[0 0 1][ ] ]//GaAs(0 0 1)[1 1 0] . The frequency dispersion of the measured capacitance-voltage (C-V) curves of the single crystal ALD-Y2O3/GaAs(0 0 1)-4 × 6 is ∼7% for p-GaAs and ∼14% for n-GaAs (1 M Hz to 100 Hz), lowest ever achieved in the ALD-oxides on GaAs(0 0 1).
    Microelectronic Engineering 04/2015; 147. DOI:10.1016/j.mee.2015.04.061 · 1.34 Impact Factor
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    ABSTRACT: The electronic structure of single-crystal (In)GaAs deposited with tri-methylaluminum (TMA) and water via atomic layer deposition (ALD) is presented with high-resolution synchrotron radiation core-level photoemission and capacitance-voltage (CV) characteristics. The interaction of the precursor atoms with (In)GaAs is confined at the topmost surface layer. The Ga-vacant site on the GaAs(111)A-2 × 2 surface is filled with Al, thereby effectively passivating the As dangling bonds. The As-As dimers on the GaAs(001)-2 × 4 surface are entirely passivated by one cycle of TMA and water. The presumed layerwise deposition fails to happen in GaAs(001)-4 × 6. In In0.20Ga0.80As(001)-2 × 4, the edge row As atoms are partially bonded with the Al, and one released methyl then bonds with the In. It is suggested that the unpassivated surface and subsurface atoms cause large frequency dispersions in CV characteristics under the gate bias. We also found that the (In)GaAs surface is immune to water in ALD. However, the momentary exposure of it to air (less than one minute) introduces significant signals of native oxides. This indicates the necessity of in situ works of high κ/(In)GaAs-related experiments in order to know the precise interfacial atomic bonding and thus know the electronic characteristics. The electric CV measurements of the ALD-Al2O3 on these (In)GaAs surfaces are correlated with their electronic properties.
    Nanotechnology 03/2015; 26(16):164001. DOI:10.1088/0957-4484/26/16/164001 · 3.67 Impact Factor
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    ABSTRACT: Molecular beam epitaxy deposited rare-earth oxide of Y2O3 has effectively passivated GaSb, leading to low interfacial trap densities of (1–4) × 1012 cm−2 eV−1 across the energy bandgap of GaSb. A high saturation drain current density of 130 μA/μm, a peak transconductance of 90 μS/μm, a low subthreshold slope of 147 mV/decade, and a peak field-effect hole mobility of 200 cm2/V-s were obtained in 1 μm-gate-length self-aligned inversion-channel GaSb p-Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs). In this work, high-κ/GaSb interfacial properties were better in samples with a high substrate temperature of 200 °C than in those with high κ's deposited at room temperature, in terms of the interfacial electrical properties, particularly, the reduction of interfacial trap densities near the conduction band and the MOSFET device performance.
    Applied Physics Letters 11/2014; 105(18):182106. DOI:10.1063/1.4901100 · 3.52 Impact Factor
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    ABSTRACT: We performed spin pumping experiment on high quality, epitaxial Fe3Si/GaAs structures grown by molecular beam epitaxy. By tailoring the thickness and doping (n, p) level of the conducting GaAs epi-layer, thermal heating common of ferromagnetic metal/semiconductor heterostructure was removed effectively. A large inverse spin Hall Effect (ISHE) voltage up to 49.2 mu V was observed for Fe3Si/p-GaAs. Smaller ISHE voltage (V-ISHE) by a factor of similar to 0.4 was obtained for Fe3Si/n-GaAs, as scaled with its resistivity. By taking into account of the "self-induced" ISHE apparently observed in our samples, the minimum value of spin Hall angle theta(ISHE) for n-GaAs and p-GaAs was estimated to be 1.9 x 10(-4) and 2.8 x 10(-5), respectively. (C) 2014 AIP Publishing LLC.
    Applied Physics Letters 10/2014; 105(15). DOI:10.1063/1.4898781 · 3.52 Impact Factor
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    ABSTRACT: A high-quality high-κ/Ge interface has been achieved by combining molecule beam epitaxy grown Ge epitaxial layer and in-situ deposited high κ dielectric. The employment of Ge epitaxial layer has sucessfully buried and/or removed the residue of unfavorable carbon and native oxides on the chemically cleaned and ultra-high vacuum annealed Ge(100) wafer surface, as studied using angle-resolved x-ray photoelectron spectroscopy. Moreover, the scanning tunneling microscopy analyses showed the significant improvements in Ge surface roughness from 3.5 Å to 1 Å with the epi-layer growth. Thus, chemically cleaner, atomically more ordered, and morphologically smoother Ge surfaces were obtained for the subsquent deposition of high κ dielectrics, comparing with those substrates without Ge epi-layer. The capacitance-voltage (C-V) characteristics and low extracted interfacial trap density (Dit) reveal the improved high-κ/Ge interface using the Ge epi-layer approach.
    Applied Physics Letters 05/2014; 104(20):202102-202102-5. DOI:10.1063/1.4879022 · 3.52 Impact Factor
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    ABSTRACT: In-situ atomic layer deposited (ALD)-HfO2 has been used to passivate In0.53Ga0.47As. Atom-to-atom interactions for the interfacial electronic/chemical characteristics of in-situ ALD-HfO2 on pristine molecular beam epitaxy (MBE) grown In0.53Ga0.47As surface have been studied using synchrotron-radiation photoemission (SRPES). ALD-HfO2/In0.53Ga0.47As metal-oxide-semiconductor capacitors (MOSCAPs) have exhibited excellent capacitance-voltage (C-V) characteristics. The interfacial trap density spectra in absence of mid-gap peaks were attained. Moreover, 1 m-gate-length self-aligned inversion-channel In0.53Ga0.47As MOS field-effect-transistors (MOSFETs) using in-situ ALD-HfO2 as the gate dielectric have achieved record-high maximum drain current (I-D) of 1.5 mA/mu m and peak transconductance (G(m)) of 0.84 mS/mu m. Moreover, low contact resistivity (rho(c)) of 6.7x10(-9) Omega-cm(2) by inserting a 0.6 nm ZnO dielectric layer between titanium metal and InGaAs (with Si doping concentration of 1.5x10(19) cm(-3)) has been demonstrated; this contact structure was employed in the source/drain on the implant-free In0.53Ga0.47As quantum-well MOSFETs to obtain peak G(m) of 1.25 mS/mu m and low source/drain resistance of 190 Omega-mu m.
    ECS Transactions 03/2014; 61(2):113-124. DOI:10.1149/06102.0113ecst
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    ABSTRACT: The growth of a passivating layer on a In0.53Ga0.47As(001)-4 × 2 surface by atomic-layer deposition of tetrakis[ethylmethylamino]Hafnium (TEMAHf)) followed by the water pulse was investigated by synchrotron radiation photoemission. The Hf atoms maintain four-fold coordination, both after the initial TEMAHf deposition and the subsequent water pulse. The Hf atoms initially bond to the As dangling bonds of the surface As atom located on the edges of the raised ridges. One EMA ligand is removed in this process. Subsequent water exposure substitutes OH ligand for one or more remaining EMA ligands. These in turn react with TEMAHf to form Hf-O-Hf bonds allowing the hafnium oxides to grow. The surface In atoms on the terrace of the raised ridges were partially removed, but none bonded of the precursor atoms. Correlations between the interfacial electronic structure and the electric performance are discussed.
    Applied Physics Letters 01/2014; 104(4):042904-042904-5. DOI:10.1063/1.4863440 · 3.52 Impact Factor
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    ABSTRACT: Self-aligned inversion-channel In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors (MOSFETs) have been fabricated using the gate dielectrics of in-situ directly atomic-layer-deposited (ALD) HfO2 followed by ALD-Al2O3. There were no surface pretreatments and no interfacial passivation/barrier layers prior to the ALD. TiN/Al2O3 (4 nm)/HfO2 (1 nm)/In0.53Ga0.47As/InP MOS capacitors exhibited well-behaved capacitance-voltage characteristics with true inversion behavior, low leakage current densities of ∼10-8 A/cm2 at ±1 MV/cm, and thermodynamic stability at high temperatures. Al2O3 (3 nm)/HfO2 (1 nm)/In0.53Ga0.47As MOSFETs of 1 μm gate length, with 700 °C–800 °C rapid thermal annealing in source/drain activation, have exhibited high extrinsic drain current (ID) of 1.5 mA/μm, transconductance (Gm) of 0.84 mS/μm, ION/IOFF of ∼104, low sub-threshold swing of 103 mV/decade, and field-effect electron mobility of 1100 cm2/V · s. The devices have also achieved very high intrinsic ID and Gm of 2 mA/μm and 1.2 mS/μm, respectively.
    Applied Physics Letters 12/2013; 103(25):253509-253509-5. DOI:10.1063/1.4852975 · 3.52 Impact Factor
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    ABSTRACT: The surface As/Ga atoms 3d core-level spectra of the atomically clean GaAs(1 1 1)A-2 × 2, GaAs(0 0 1)-2 × 4, and GaAs(0 0 1)-4 × 6 surfaces were firstly presented using high-resolution synchrotron radiation photoemission as a probe. The technique clearly explicates behaviors of the As atoms in different surface reconstruction. For GaAs(1 1 1)A-2 × 2, the surface As sits in the same plane as the Ga atoms. As to the GaAs(0 0 1)-2 × 4 surface, the As-As dimers dominate the surface layer, while for GaAs(001)-4 × 6, the As existed in two forms, the As in the As-Ga dimer and the 3-fold coordinated As. Next, we present a microscopic view of in situ atomic layer deposition (ALD) of Al2O3 on GaAs taking the two (0 0 1) surfaces as examples. The precursors were trimethylaluminum (TMA) and water. TMA could exist in either a chemisorbed or physisorbed form, depending on the charge environment of the associated surface atoms. The subsequent water purge resulted in both adsorbed forms being etched off or transformed the physisorbed TMA into the As-O-Al(CH3)2 configuration. We found that the ALD process rendered the precursors partially and selectively in forming bonds with the surface atoms without disturbing the atoms in the subsurface layer. Upon annealing, the interfacial bonding was dominated with the Assbnd Al as well as Gasbnd O bonds.
    Applied Surface Science 11/2013; 284:601-610. DOI:10.1016/j.apsusc.2013.07.140 · 2.54 Impact Factor
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    ABSTRACT: In atomic-layer deposition (ALD), organoaluminum as trimethyl-aluminum (TMA) on a freshly molecular beam epitaxy grown In0.20Ga0.80As(001)-4 × 2 surface has three forms: Al bonding with 1, 2, and 3 methyl groups. The ALD method of using one pulse (0.1 s) of TMA plus one pulse (0.1 s) of water was ineffective in passivating the surface, as demonstrated by the increased intensity of the reacted surface components with high numbers of pulses. The intact TMA was physisorbed on the trough In atoms, while the methyl-deficient precursors are either bridged with two As atoms or on the row-edge As atoms. After the water pulse on the TMA-covered surface, a bond in the bridged As atoms was scissored off to produce the As-Al-CH3 and As-OH, and the physisorbed TMA was unaffected. TMA removed some row In atoms, which allowed the In and Ga atoms in the second layer to form OH bonds after the water exposure. The appearance of the As-OH bonds may cause interfacial defect density (Dit) a peak at the midgap.
    Journal of Applied Physics 05/2013; 113(20). DOI:10.1063/1.4807400 · 2.19 Impact Factor
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    ABSTRACT: The structural and magnetic properties of high κ dilute magnetic oxides (DMOs) have been studied in two types of samples: thin films and nanocrystals, including Co doped HfO2 films, Co doped Y2O3 films, Co doped Y2O3 nanocrystals, and Mn doped Y2O3 nanocrystals. The characterizations were conducted by extended x-ray absorption fine structure, x-ray absorption near edge structure, and superconducting quantum interference device vibrating sample magnetometer. Oxygen vacancies are shown to play a crucial role in ferromagnetic ordering, as defect centers in the bound magnetic polaron model to account for DMOs with medium band gap and low carrier concentration. The observation of room temperature ferromagnetism in tri-valence oxide of Y2O3 as well as in tetra-valence oxide of HfO2 suggests a generic feature of transition metal doped high κ oxides as good candidates for DMO. The ability to modulate the magnetic behavior of DMO via oxygen vacancy concentration by means of post anneals can be exploited for potential applications in spintronics.
    Journal of Applied Physics 04/2013; 113(17). DOI:10.1063/1.4799613 · 2.19 Impact Factor
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    ABSTRACT: Spin pumping transfers the spin momentum of the magnetization precession to the conduction electrons and forms pure spin currents, and was investigated in the ferromagnetic epitaxial Fe3Si films and polycrystalline Py films covered with normal metal (Pt, Au) overlayers, respectively. With the applied microwave applied from a cavity and an in-plane magnetic field, an electric voltage due to inverse spin-Hall effect is detected under the ferromagnetic resonance condition. A linear relationship between the measured voltage and microwave power has been obtained, consistent with a theoretical model. The spin Hall angles of Pt and Au as deduced from the present Py and Fe3Si data are in agreement with the published values. A very large voltage signal is observed for Fe3Si/Au film with in-situ capping of Au, suggesting the possibility of the future applications for the spintronic devices.
    Journal of Applied Physics 04/2013; 113(17). DOI:10.1063/1.4799147 · 2.19 Impact Factor
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    ABSTRACT: Inversion-channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) have been fabricated using in-situ molecular beam deposited Al2O3 as a gate dielectric directly on freshly molecular beam epitaxy grown Ga-stabilized (4 × 6) and As-covered c(4 × 4) GaAs(100) reconstructed surfaces. The MOSFET using the former surface gives a drain current (Id) of 92 μA/μm and a transconductance (Gm) of 43 μS/μm in an 1 μm gate length configuration; these values are more than 100 times higher than those attained in the MOSFET using the latter surface, which has an Id of 0.47 μA/μm and a Gm of 0.45 μS/μm. The enhancement of the inversion currents and Gm may indicate Fermi-level unpinning at the oxide/GaAs(100) interface. The result further confirms that the mid-gap interfacial trap densities of 2 × 1012 eV−1 cm−2 and of exceeding 1013 eV−1cm−2 in the samples on the Ga-stabilized and the As-covered GaAs(100) surfaces, respectively, are correlated to the inversion-channel device performance.
    Applied Physics Letters 03/2013; 102(9). DOI:10.1063/1.4793433 · 3.52 Impact Factor
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    ABSTRACT: Two different types of lasing modes, vertical Fabry-Perot cavity and random lasing, were observed in ZnO epi-films of different thicknesses grown on Si (111) substrates. Under optical excitation at room temperature by a frequency tripled Nd:YVO<sub>4</sub> laser with wavelength of 355 nm, the lasing thresholds are low due to high crystalline quality of the ZnO epitaxial films, which act as microresonators. For the thick ZnO layer (1,200 nm), its lasing action is originated from the random scattering due to the high density of crack networks developed in the thick ZnO film. However, the low crack density of the thin film (555 nm) fails to provide feedback loops essential for random scattering. Nevertheless, even the lower threshold lasing is achieved by the Fabry-Perot cavity formed by two interfaces of the thin ZnO film. The associated lasing modes of the thin ZnO film can be characterized as the transverse Gaussian modes attributed to the smooth curved surfaces.
    Optics Express 01/2013; 21(2):1857-64. DOI:10.1364/OE.21.001857 · 3.53 Impact Factor
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    ABSTRACT: A microscopic view of in situ atomic layer deposition Al2O3 on clean n-GaAs (001)-4 × 6 surfaces probed by high-resolution synchrotron radiation photoemission is presented. The precursors of trimethylaluminum (TMA) and water partially and selectively bond with the surface atoms without disturbing the atoms in the subsurface layer. The first-cycle TMA acts differently on the surface As atoms; namely, TMA is dissociative on As in the As-Ga dimer but is physisorbed on As that is 3-fold Ga coordinated. Water drastically alters the TMA-covered surface to etch off the dissociated TMA with As, giving Ga–O bonding for the later deposition of Al2O3 and at the same time to transform the configuration of the physisorbed TMA to bond strongly with As. Approximately six cycles of purges (TMA + water) are required before the interaction at the interface is complete. In comparison, the e-beam deposition of Al2O3 on GaAs greatly disturbs the III-V surface so that a high As 4+ charge state appears and the surface Ga atoms become clustered.
    Applied Physics Letters 11/2012; 101(21). DOI:10.1063/1.4767129 · 3.52 Impact Factor
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    ABSTRACT: The evolution of the strain state as a function of layer thickness of (0001) oriented ZnO epitaxial films grown by pulsed-laser deposition on Si (111) substrates with a thin oxide Y2O3 buffer layer was investigated by high resolution X-ray diffraction (XRD). The ZnO layers experience a tensile strain, which gradually diminishes with increasing layer thickness. Regions with a nearly strain-free lattice develop as the layer thickness exceeds a critical value and are correlated with the emergence of the <110> oriented crack channels. The influence of the biaxial strain to the vibrational and optical properties of the ZnO layers were also studied by micro-Raman, optical reflectance, and photoluminescence. The deformation-potential parameters, aλ and bλ, of the E2(high) phonon mode are determined to be −740.8 ± 8.4 and −818.5 ± 14.8 cm−1, respectively. The excitonic transitions associated with the FXA, FXB, and D°XA emissions and the A-exciton binding energy all show linear dependence on the in-plane strain with a negative slope.
    CrystEngComm 10/2012; 14(23):8103-8109. DOI:10.1039/C2CE26074C · 3.86 Impact Factor
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    ABSTRACT: High κ gate dielectrics of HfO2 and Al2O3 were deposited on molecular beam epitaxy-grown In0.2Ga0.8As pristine surface using in-situ atomic-layer-deposition (ALD) without any surface treatment or passivation layer. The ALD-HfO2/p-In0.2Ga0.8As interface showed notable reduction in the interfacial density of states (Dit), deduced from quasi-static capacitance-voltage and conductance-voltage (G-V) at room temperature and 100 °C. More significantly, the midgap peak commonly observed in the Dit(E) of ALD-oxides/In0.2Ga0.8As is now greatly diminished. The midgap Dit value decreases from ≥15 × 1012 eV−1 cm−2 for ALD-Al2O3 to ∼2–4 × 1012 eV−1 cm−2 for ALD-HfO2. Further, thermal stability at 850 °C was achieved in the HfO2/In0.2Ga0.8As, whereas C-V characteristics of Al2O3/p-In0.2Ga0.8As degraded after the high temperature annealing. From in-situ x-ray photoelectron spectra, the AsOx, which is not the oxidized state from the native oxide, but is an induced state from adsorption of trimethylaluminum and H2O, was found at the ALD-Al2O3/In0.2Ga0.8As interface, while that was not detected at the ALD-HfO2/In0.2Ga0.8As interface.
    Applied Physics Letters 10/2012; 101(17). DOI:10.1063/1.4762833 · 3.52 Impact Factor
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    ABSTRACT: Extensive structural analysis and magnetic properties are reported on cluster free, dilute magnetic oxide of Co doped Y2O3 (Co:Y2O3) film by low temperature deposition and characterized by extended x-ray absorption fine structure, x-ray absorption near edge structure, magnetometer, and x-ray magnetic circular dichroism. Room temperature ferromagnetism was observed, and the saturation magnetic moment was modulated by oxygen vacancy concentration through post annealing process. Oxygen vacancies are shown to play a crucial role in ferromagnetic ordering, as defect centers in the bound magnetic polaron model to account for this dilute magnetic oxide of medium band gap with low carrier concentration.
    Applied Physics Letters 10/2012; 101(16). DOI:10.1063/1.4760284 · 3.52 Impact Factor

Publication Stats

8k Citations
822.80 Total Impact Points

Institutions

  • 2011–2015
    • National Taiwan University
      • • Graduate Institute of Applied Physics
      • • Department of Physics
      T’ai-pei, Taipei, Taiwan
  • 2005–2012
    • National Tsing Hua University
      • Department of Materials Science and Engineering
      Hsin-chu-hsien, Taiwan, Taiwan
  • 2008
    • Tsinghua University
      • School of Materials Science and Engineering
      Peping, Beijing, China
  • 2001–2002
    • National Sun Yat-sen University
      Kao-hsiung-shih, Kaohsiung, Taiwan
  • 1999
    • University of California, Santa Barbara
      Santa Barbara, California, United States
  • 1990–1999
    • AT&T Labs
      Austin, Texas, United States
  • 1998
    • Seoul National University
      • Department of Electrical and Computer Engineering
      Seoul, Seoul, South Korea
  • 1994–1997
    • Cornell University
      • Department of Electrical and Computer Engineering
      Ithaca, NY, United States
  • 1992
    • National Cheng Kung University
      • Department of Electrical Engineering
      臺南市, Taiwan, Taiwan
  • 1980–1991
    • University of California, Berkeley
      • • Department of Electrical Engineering and Computer Sciences
      • • Lawrence Berkeley Laboratory
      Berkeley, MO, United States
  • 1989
    • Carnegie Mellon University
      • Department of Electrical and Computer Engineering
      Pittsburgh, Pennsylvania, United States