M. Hong

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

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Publications (421)781.03 Total impact

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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 01/2014; 104(20):202102-202102-5. · 3.52 Impact Factor
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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. · 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; · 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). · 2.21 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). · 2.21 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). · 2.21 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). · 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. · 3.55 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 01/2013; 103(25):253509-253509-5. · 3.52 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). · 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. · 3.88 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). · 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). · 3.52 Impact Factor
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    ABSTRACT: Defect engineering techniques have been employed to generate and remove oxygen vacancy defects in nanoparticles of Y2O3:Mn diluted magnetic oxide (DMO). These samples were prepared by thermal decomposition method followed by a series of thermal annealing in oxygen and forming gas. The x-ray absorption analysis reveals that O vacancies surrounding Mn and Y atoms were appreciably increased by forming-gas-annealing and decreased by oxygen-annealing, accompanied by enhanced and reduced saturation magnetization as demonstrated by magnetic measurements, respectively. Our results demonstrate strong correlation between magnetism and O vacancies and therefore strongly support the bound magnetic polaron model for these high-k DMOs.
    Applied Physics Letters 07/2012; 101(2). · 3.52 Impact Factor
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    ABSTRACT: High κ dielectric of HfAlO/HfO2 was an in-situ atomic-layer-deposited directly on molecular beam epitaxy grown In0.53Ga0.47As surface without using pre-treatments or interfacial passivation layers, where HfAlO (HfO2:Al2O3 ∼ 4:1) with high re-crystallization temperature was employed as the top oxide layer. The HfAlO (∼4.5 nm)/HfO2 (0.8 nm)/In0.53Ga0.47As metal oxide semiconductor capacitors have exhibited an oxide/In0.53Ga0.47As interface free of arsenic-related defective bonding, thermodynamic stability at 800 °C, and low leakage current densities of <10−7 A/cm2 at ±1 MV/cm. The interfacial trap density (Dit) spectra in absence of mid-gap peaks were obtained by temperature-dependent capacitance and conductance with Dit’s of 2–3 × 1012 eV−1 cm−2 below and 6–12 × 1011 eV−1 cm−2 above the mid-gap of In0.53Ga0.47As, respectively. An equivalent oxide thickness of less than 1 nm has been achieved by reducing the HfAlO thickness to ∼2.7 nm with the same initial HfO2 thickness of ∼0.8 nm.
    Applied Physics Letters 04/2012; 100(17). · 3.52 Impact Factor
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    ABSTRACT: Ga2O3(Gd2O3) [GGO] 3.5 nm-thick, with an in situ Al2O3 cap 1.5 nm thick, has been directly deposited on Ge substrate without employing interfacial passivation layers. The equivalent oxide thickness (EOT) of the gate stack is 1.38-nm. The metal-oxide-semiconductor (MOS) capacitors using Al2O3/GGO as the gate dielectric have given capacitance–voltage characteristics with frequency dispersions of ∼4% at accumulation (10 kHz–1 MHz) and frequency dependent flat-band voltage shift (∼30 mV). The dielectric constant of the GGO remains at 14–15. Furthermore, the TiN/Al2O3/GGO/Ge pMOSFET with a gate length of 1 μm has given a saturation drain current density, a maximum transconductance and a field-effect hole mobility of 800 μA/μm, 423 μS/μm, and 300 cm2/V s, respectively.
    Microelectronic Engineering 03/2012; 91:89–92. · 1.22 Impact Factor
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    ABSTRACT: The structural, optical and electrical properties of the c-plane ZnO epitaxial films grown by pulsed laser deposition on a Si(111) substrate buffered with a thin layer of γ-Al2O3 were investigated by X-ray diffraction, transmission electron microscopy, photoluminescence (PL) and Hall measurements. Detailed structural investigation showed that the dominant structural defects in the ZnO films are threading dislocations (TDs). Experimental results manifest the edge- and screw-type of TDs influence the optical and electric properties differently; the intensity ratio between the PL yellow-green band to near band edge emission and the carrier concentration are affected mainly by the edge TD, and the FWHM of the near band edge emission is dominantly influenced by the screw TD.
    CrystEngComm 02/2012; 14(5):1665-1671. · 3.88 Impact Factor
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    ABSTRACT: High-κ dielectrics on high carrier mobility channels, such as InxGa1-xAs, are now being considered for CMOS technology beyond 15 nm node. The initial bonding of high-κ/InGaAs determines the value and the distribution of interfacial density of states (Dit) within the InxGa1-xAs band gap, key to the device performance. In this work, atomic layer deposited (ALD) HfO2 and Al2O3 on MBE-grown InxGa1-xAs (001) have been in-situ and ex-situ carried out to investigate the initial stage of interfacial reactions by high resolution photoemission spectroscopy using synchrotron radiation and monochromatic Al Ka x-ray sources. Comparing the results with the corresponding electrical measurements (C-V and G-V at various temperatures), Fermi level unpinning in the oxide/InxGa1-xAs hetero-structure may be attributed to the exclusion of the As-As and the As-O bonding during the initial interfacial formation.
    02/2012;
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    ABSTRACT: The semiconductor industry is calling for innovative devices offering high performance with low power consumption. High-κ dielectrics/metal gates on high carrier mobility channels are now strong contenders in the post Si CMOS application. Hafnium-based oxide has been employed as the gate dielectric in Si CMOS since 45 nm node and InGaAs is a leading candidate for channel materials. However, reports of HfO2 on InGaAs are scant, and surface treatments using H2S or trimethylaluminum are claimed to be required for achieving high quality HfO2(high-κ)/InGaAs interface. In this work, HfO2 has been in-situ deposited on n- and p-In0.53Ga0.47As using both molecular-beam-epitaxy (MBE) and atomic-layer- deposition (ALD), without using any interfacial passivation layer or surface treatments. The HfO2/In0.53Ga0.47As metal-oxide-semiconductor capacitors (MOSCAPs) all exhibit outstanding thermal stabilities (> 800^oC), low leakage currents (˜ 10-8 A/cm^2 at 1 MV/cm), and good CV characteristics. Moreover, the MOSCAPs have shown spectra of interfacial trap densities (Dit's) with no discernible peaks at mid-gap, confirmed by temperature-dependent conductance method.
    02/2012;
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    ABSTRACT: Direct measurements of atomic-scale electronic structure at nm-thick epitaxial Gd2O3 gate oxides on GaAs have been performed using cross-sectional scanning tunneling microscopy and spectroscopy. Both scanning tunneling spectroscopy and analysis of the local electronic states across the gate oxides suggest the Ga-O terminated hetero-interface. In addition, along with the theoretical modeling, the band offsets for both conduction and valence states are identified. A unique combination of STM and STS successfully provides direct information on the interfacial band profile and band offsets across the model high-κ/III-V system in the work.
    02/2012;

Publication Stats

4k Citations
781.03 Total Impact Points

Institutions

  • 2011–2014
    • National Taiwan University
      • Graduate Institute of Applied Physics
      T’ai-pei, Taipei, Taiwan
  • 2006–2012
    • National Tsing Hua University
      • Department of Materials Science and Engineering
      Hsin-chu-hsien, Taiwan, Taiwan
    • National Chiao Tung University
      • Department of Electronics Engineering
      Hsinchu, Taiwan, Taiwan
  • 1997–2002
    • National Sun Yat-sen University
      • Department of Physics
      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
  • 1990–1998
    • National Cheng Kung University
      • • Department of Physics
      • • Department of Electrical Engineering
      Tainan, Taiwan, Taiwan
  • 1994–1997
    • Cornell University
      • Department of Electrical and Computer Engineering
      Ithaca, NY, United States
    • Sandia National Laboratories
      Albuquerque, New Mexico, United States
  • 1989–1993
    • University of Nebraska at Lincoln
      Lincoln, Nebraska, United States
  • 1980–1993
    • University of California, Berkeley
      • • Department of Electrical Engineering and Computer Sciences
      • • Lawrence Berkeley Laboratory
      Berkeley, MO, United States
  • 1988–1989
    • Carnegie Mellon University
      • Department of Electrical and Computer Engineering
      Pittsburgh, Pennsylvania, United States
  • 1984
    • University of Colorado at Boulder
      Boulder, Colorado, United States