M.C. Ho

Texas Instruments Inc., Dallas, Texas, United States

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Publications (15)20.28 Total impact

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    ABSTRACT: Next-generation power amplifiers must operate at lower supply voltages without sacrificing linearity or efficiency. GaInP/GaAs double-heterojunction bipolar transistors with GaInP collectors can improve over GaAs single-heterojunction bipolar transistors (HBTs) in power-amplifier applications, based on lower offset voltage, increased breakdown electric field, and absence of saturation charge storage. To best exploit these characteristics, amplifier architectures that employ HBTs in switching mode can be used
    IEEE Transactions on Microwave Theory and Techniques 09/1999; · 2.23 Impact Factor
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    ABSTRACT: AlGaAs/GaAs n-p-n heterojunction bipolar transistors (HBTs) fabricated using an Si-implant to form the subcollector followed by MOCVD growth of the remaining structure are demonstrated. The common emitter current gain of large test devices is ~50 at a collector current density of 1.9×10<sup>3</sup> A/cm<sup>2</sup>. The base-collector and emitter-base current ideality factors are 1.08 and 1.26, respectively. Co-implantation with Se reduced the subcollector sheet resistance to 13 Ω/&square;. Patterning of this implanted subcollector results in a significant reduction of extrinsic base-collector capacitance (C<sub>hc</sub>)
    Electronics Letters 06/1998; · 1.04 Impact Factor
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    ABSTRACT: Low-base-collector capacitance (C/sub bc/) AlGaAs/GaAs HBTs with f/sub MAX/>200 GHz and f/sub T/=52 GHz have been fabricated. With co-implants of high energy, high dose He/sup +/ and H/sup +/ ions through the external base layer, part of the heavily doped n/sup +/ sub-collector was compensated leading to a decrease in the extrinsic portion of C/sub bc/. The implants caused only a slight increase of base resistance. Using this approach in combination with a standard low dose, shallow collector compensating implant, C/sub bc/ of double implanted HBT's can be reduced by more than 35%.< >
    IEEE Electron Device Letters 12/1995; · 2.79 Impact Factor
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    ABSTRACT: In this paper we present a novel technique which can significantly reduce the base-collector capacitance (C<sub>bc</sub>) in AlGaAs/GaAs HBTs. C<sub>bc</sub>, is a key limiter of HBT microwave gain and bandwidth. Our process uses high dose, high-energy ion implantation through the external base layer to compensate part of the heavily doped sub-collector. It also uses the more conventional self-aligned shallow implant to compensate the entire collector underneath the base contact. The total C<sub>bc</sub> of the double implanted HBTs has been reduced by more than 35% with this new technique as compared to devices with shallow implant only. Under proper conditions, the double implantation produces little damage to the base (which can cause an increase in base resistance R<sub>B</sub>); thus the RF performance can be significantly improved. An f<sub>MAX</sub> greater than 200 GHz has been obtained, comparable to the best previous reported results in common emitter HBTs
    Device Research Conference, 1995. Digest. 1995 53rd Annual; 07/1995
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    ABSTRACT: Electron and hole impact ionization coefficients in (100)Ga 0.5 In 0.5 P have been measured by photomultiplication measurements. The ratio of hole to electron ionization coefficients, β/α, is shown to decrease from 2 to 1 when the electric field is increased from 3.5×10<sup>5</sup> to 6.5×10<sup>5</sup> V/cm. As confirmation, breakdown voltages were measured for several p<sup>+</sup>-n<sup>-</sup>-n<sup>+</sup> diodes with various concentrations in the n<sup>-</sup> region. The values observed showed good agreement with those calculated from the ionization coefficients. Typical breakdown voltages are on the order of 1.6 times higher than those expected for GaAs. © 1995 American Institute of Physics.
    Applied Physics Letters 07/1995; · 3.52 Impact Factor
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    ABSTRACT: Novel InP-based heterojunction bipolar transistors (HBTs) using an AlInP pseudomorphic emitter, together with an InP base and collector, have been fabricated. By using InP as both base and collector, the advantage of high electron velocity and high breakdown field of InP collectors are obtained without the problem associated with the energy barrier between the more standard InGaAs/InP base and collector heterojunction. Epitaxial layers were grown by gas-source molecular beam epitaxy (GSMBE). The 200 Å pseudomorphic emitter had an aluminium fraction of 15%, sufficiently suppressing hole injection from the base. The DC gain for 40×40 μm<sup>2</sup> devices reached 18. The breakdown voltage BV<sub>CEO</sub> of 10 V is an improvement over devices with InGaAs base and collector layers
    Electronics Letters 02/1995; · 1.04 Impact Factor
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    ABSTRACT: First Page of the Article
    Device Research Conference, 1994. 52nd Annual; 02/1994
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    ABSTRACT: The profiles of AlGaAs/GaAs heterostructures grown by gas‐source molecular beam epitaxy (GSMBE) on patterned substrates at different growth temperatures have been studied. It was found that at higher substrate temperature, the GSMBE growth results in Al clustering and the formation of high index planes. With a proper combination of low growth temperature and etched profile, a quasiplanarized surface is obtainable. A process simulation program is found to be capable of simulating the GSMBE growth profile at lower substrate temperature with reasonable accuracy.
    Journal of Applied Physics 09/1993; · 2.21 Impact Factor
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    ABSTRACT: The growth behavior of Ar-ion-laser-assisted metalorganic molecular beam epitaxy (MOMBE) of (001) GaAs, in the temperature range 330–450°C with triethylgallium (TEGa) and As4, was studied by monitoring the specular-beam intensity oscillations of reflection high-energy electron diffraction (RHEED), with the laser turned on and off. The decomposition rate of TEGa is enhanced under Ar+ laser irradiation. The Ar+ laser also enhances the surface migration of adsorbates and arsenic desorption. In the arsenic-controlled growth regime, the growth rate increases monotonically at low laser power and tends to saturate at high laser power due to a balance between enhanced decomposition of TEGa and desorption of arsenic.
    Journal of Crystal Growth 11/1992; 124(s 1–4):181–185. · 1.55 Impact Factor
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    ABSTRACT: Not Available
    Metalorganic Vapor Phase Epitaxy, 1992. Sixth International Conference; 07/1992
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    ABSTRACT: The effective Schottky barrier height on n-type InP is increased by a thin heavily-doped p-type surface layer grown by gas-source molecular beam epitaxy. The relationships between the barrier height increment and the doping level and thickness of the surface layer have been studied. The Schottky diodes fabricated by this method show reasonably low leakage current at high reverse bias and high reverse breakdown voltage.
    Electronics Letters 02/1992; · 1.04 Impact Factor
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    ABSTRACT: In this article, we report a study of incorporation behavior of the phosphorus in GaAs1-xPx during gas‐source molecular beam epitaxial growth under various experimental conditions. The phosphorus composition in GaAsP was found to be generally different from the phosphine flow‐rate fraction in the gas phase, and it is independent of the V/III incorporation ratio. This composition, however, agrees with the group‐V‐induced reflection high‐energy electron diffraction oscillation determination. An increase of the phosphorus composition occurs at the substrate temperature region between 520 and 620 °C, attributable to different desorption kinetics of As and P. The same phosphorus incorporation into GaAsP under different strain states was found when the GaAsP layer was pseudomorphically grown on GaAs and GaP substrates.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/1992; 10:953-955. · 1.36 Impact Factor
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    ABSTRACT: Phosphorus‐controlled growth rate of homoepitaxial (100) InP, GaP, and AlP on GaP substrates by gas source molecular beam epitaxy was investigated. Elemental group‐III sources and thermally cracked phosphine were used. The growth rate was monitored by the specular beam intensity oscillations of reflection high‐energy electron diffraction. This technique gives exact values of V/III ratio on the surface by measuring the amount of phosphorus which is actually incorporated into the film. Here the V/III ratio is defined as P‐controlled growth rate divided by group‐III‐controlled growth rate instead of the beam flux V/III ratio. Also the phosphorus surface desorption activation energies were measured to be 0.61 eV and in the range between 0.89 and 0.97 eV for InP and GaP, respectively.
    Applied Physics Letters 02/1991; · 3.52 Impact Factor
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    ABSTRACT: Not Available
    Epitaxial Materials and In-Situ Processing for Optoelectronic Devices, 1991/Microfabrication for Photonics and Optoelectronics, 1991. LEOS 1991 Summer Topical Meetings on; 01/1991
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    ABSTRACT: We demonstrate the first small area emitter (1.4 × 3 µm 2 ) N-p-n AlGaAs/GaAs HBTs fabricated with N + - + implants of various doses and energies on a semi-insulating GaAs substrate, and the remaining HBT layers were grown by MOCVD. To evaluate the impacts of Cbc reduction, devices with varying subcollector areas were fabricated for comparison. Small signal s- parameter data was measured to extract fT, fmax and Cbc. By varying the implanted subcollector area, the base- collector capacitance Cbc was reduced by almost 40% using this manufacturable process. The common emitter current gain of devices fabricated by this implant/epitaxial hybrid process is about 50 which is similar to our baseline device, indicating good material quality using this technique.

Publication Stats

86 Citations
20.28 Total Impact Points

Institutions

  • 1995
    • Texas Instruments Inc.
      Dallas, Texas, United States
  • 1991–1995
    • University of California, San Diego
      • Department of Electrical and Computer Engineering
      San Diego, CA, United States
  • 1994
    • Hitachi, Ltd.
      Edo, Tōkyō, Japan