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Milton Feng - One of the best experts on this subject based on the ideXlab platform.

  • 12 5 nm base pseudomorphic heterojunction Bipolar Transistors achieving ft 710ghz and fmax 340ghz
    Applied Physics Letters, 2005
    Co-Authors: W Hafez, William Snodgrass, Milton Feng
    Abstract:

    The pseudomorphic collector structure is known to allow enhanced collector transport, facilitating higher current cutoff frequencies at lower current densities and junction temperatures compared to traditional single heterojunction structures. The performance of a 0.25×3μm2 pseudomorphic heteojunction Bipolar Transistors achieves peak fT of 710 GHz (fMAX=340GHz) at a collector current density of 20mA∕μm2. The same device achieves a fT∕fMAX of 540∕407GHz at a reduced current density of 7.5mA∕μm2. The epitaxial structure employs a 12.5 nm strained InGaAs base and 55 nm InGaAs collector, and exhibits a β of 115 and breakdown voltage of BVCEO=1.75V.

  • experimental demonstration of pseudomorphic heterojunction Bipolar Transistors with cutoff frequencies above 600ghz
    Applied Physics Letters, 2005
    Co-Authors: W Hafez, Milton Feng
    Abstract:

    Pseudomorphic InP∕InGaAs heterojunction Bipolar Transistors (PHBTs) using a compositionally graded collector (10% indium grading) and graded base (6% indium grading) to reduce the transit time of the device are reported. A 0.4×6μm2 HBT achieves excellent ƒT values of 604GHz (associated ƒMAX=246GHz) at a collector current density of 16.8mA∕μm2, with a dc gain of 65 and a breakdown voltage of BVCEO=1.7V.

  • light emitting transistor light emission from ingap gaas heterojunction Bipolar Transistors
    Applied Physics Letters, 2004
    Co-Authors: Milton Feng, N Holonyak, W Hafez
    Abstract:

    This letter reports the direct observation of the radiative recombination in the graded base layer of InGaP/GaAs heterojunction Bipolar Transistors (HBTs). For a 1 μm×16 μm emitter HBT, we demonstrate the change of the spontaneous light emission intensity (ΔIout) as the base current (Δib) of the HBT is varied from 0 to 5 mA, i.e., an HBT operating as a light-emitting transistor. We also demonstrate output light modulation from the base layer at 1 MHz with the base current modulated at 1 MHz in normal transistor mode operation of the HBT.

Hinfai Chau - One of the best experts on this subject based on the ideXlab platform.

  • thermal properties and thermal instabilities of inp based heterojunction Bipolar Transistors
    IEEE Transactions on Electron Devices, 1996
    Co-Authors: Wenchau Liu, Hinfai Chau
    Abstract:

    We investigate the physical parameters which are critical to the understanding of the thermal phenomena in InP-based heterojunction Bipolar Transistors. These parameters include thermal resistance, thermal-electric feedback coefficient, current gain, and base-collector leakage current. We examine the thermal instability behavior in multi-finger HBTs, and observe for the first time the collapse of current gain in InP-based HBTs. Based on both measurement and modeling results, we establish the reasons why the collapse is rarely observed in InP HBT's, in a sharp contrast to AlGaAs/GaAs HBT's. We compare the similarities and differences on how InP-based HBT, GaAs-based HBT, and Si-based Bipolar Transistors react once the thermal instability condition is met. Finally, we describe the issues involved in the design of InP HBTs.

  • the use of base ballasting to prevent the collapse of current gain in algaas gaas heterojunction Bipolar Transistors
    IEEE Transactions on Electron Devices, 1996
    Co-Authors: Wenchau Liu, A Khatibzadeh, J Sweder, Hinfai Chau
    Abstract:

    We propose the use of base-ballasting resistance to guarantee absolute thermal stability in AlGaAs/GaAs heterojunction Bipolar Transistors (HBTs). Base-ballasted HBTs are fabricated and the measured I-V, regression and S-factor characteristics are discussed. We present a numerical model which elucidates the reasons why the base-ballasting scheme is helpful to HBTs but is damaging to silicon Bipolar Transistors. We compare measured small-signal and large-signal performances of unballasted, emitter-ballasted, and base-ballasted HBTs.

W Hafez - One of the best experts on this subject based on the ideXlab platform.

  • 12 5 nm base pseudomorphic heterojunction Bipolar Transistors achieving ft 710ghz and fmax 340ghz
    Applied Physics Letters, 2005
    Co-Authors: W Hafez, William Snodgrass, Milton Feng
    Abstract:

    The pseudomorphic collector structure is known to allow enhanced collector transport, facilitating higher current cutoff frequencies at lower current densities and junction temperatures compared to traditional single heterojunction structures. The performance of a 0.25×3μm2 pseudomorphic heteojunction Bipolar Transistors achieves peak fT of 710 GHz (fMAX=340GHz) at a collector current density of 20mA∕μm2. The same device achieves a fT∕fMAX of 540∕407GHz at a reduced current density of 7.5mA∕μm2. The epitaxial structure employs a 12.5 nm strained InGaAs base and 55 nm InGaAs collector, and exhibits a β of 115 and breakdown voltage of BVCEO=1.75V.

  • experimental demonstration of pseudomorphic heterojunction Bipolar Transistors with cutoff frequencies above 600ghz
    Applied Physics Letters, 2005
    Co-Authors: W Hafez, Milton Feng
    Abstract:

    Pseudomorphic InP∕InGaAs heterojunction Bipolar Transistors (PHBTs) using a compositionally graded collector (10% indium grading) and graded base (6% indium grading) to reduce the transit time of the device are reported. A 0.4×6μm2 HBT achieves excellent ƒT values of 604GHz (associated ƒMAX=246GHz) at a collector current density of 16.8mA∕μm2, with a dc gain of 65 and a breakdown voltage of BVCEO=1.7V.

  • light emitting transistor light emission from ingap gaas heterojunction Bipolar Transistors
    Applied Physics Letters, 2004
    Co-Authors: Milton Feng, N Holonyak, W Hafez
    Abstract:

    This letter reports the direct observation of the radiative recombination in the graded base layer of InGaP/GaAs heterojunction Bipolar Transistors (HBTs). For a 1 μm×16 μm emitter HBT, we demonstrate the change of the spontaneous light emission intensity (ΔIout) as the base current (Δib) of the HBT is varied from 0 to 5 mA, i.e., an HBT operating as a light-emitting transistor. We also demonstrate output light modulation from the base layer at 1 MHz with the base current modulated at 1 MHz in normal transistor mode operation of the HBT.

Wenchau Liu - One of the best experts on this subject based on the ideXlab platform.

  • thermal properties and thermal instabilities of inp based heterojunction Bipolar Transistors
    IEEE Transactions on Electron Devices, 1996
    Co-Authors: Wenchau Liu, Hinfai Chau
    Abstract:

    We investigate the physical parameters which are critical to the understanding of the thermal phenomena in InP-based heterojunction Bipolar Transistors. These parameters include thermal resistance, thermal-electric feedback coefficient, current gain, and base-collector leakage current. We examine the thermal instability behavior in multi-finger HBTs, and observe for the first time the collapse of current gain in InP-based HBTs. Based on both measurement and modeling results, we establish the reasons why the collapse is rarely observed in InP HBT's, in a sharp contrast to AlGaAs/GaAs HBT's. We compare the similarities and differences on how InP-based HBT, GaAs-based HBT, and Si-based Bipolar Transistors react once the thermal instability condition is met. Finally, we describe the issues involved in the design of InP HBTs.

  • the use of base ballasting to prevent the collapse of current gain in algaas gaas heterojunction Bipolar Transistors
    IEEE Transactions on Electron Devices, 1996
    Co-Authors: Wenchau Liu, A Khatibzadeh, J Sweder, Hinfai Chau
    Abstract:

    We propose the use of base-ballasting resistance to guarantee absolute thermal stability in AlGaAs/GaAs heterojunction Bipolar Transistors (HBTs). Base-ballasted HBTs are fabricated and the measured I-V, regression and S-factor characteristics are discussed. We present a numerical model which elucidates the reasons why the base-ballasting scheme is helpful to HBTs but is damaging to silicon Bipolar Transistors. We compare measured small-signal and large-signal performances of unballasted, emitter-ballasted, and base-ballasted HBTs.

  • the collapse of current gain in multi finger heterojunction Bipolar Transistors its substrate temperature dependence instability criteria and modeling
    IEEE Transactions on Electron Devices, 1994
    Co-Authors: Wenchau Liu, A Khatibzadeh
    Abstract:

    One undesirable phenomenon observed when AlGaAs/GaAs heterojunction Bipolar Transistors (HBT's) are operated under high power density is the collapse (of current gain). The collapse manifests itself by a distinct abrupt decrease of collector current in the transistor common-emitter current-voltage (I-V) characteristics. In this investigation, we study the substrate temperature dependence of the collapse. A unified equation is introduced to relate the collapse instability criterion with other thermal instability criteria proposed for silicon Bipolar Transistors. The effects of the thermal instability on the collapse behavior of 2-finger and 1-finger HBT's are examined. We also present a numerical model to adequately describe the collapse in multi-finger HBT's having arbitrary geometry. The I-V characteristics and regression plots of both ballasted and unballasted HBT's are compared. >

H Morkoc - One of the best experts on this subject based on the ideXlab platform.

  • alxga1 xas alyga1 yas and gaas pseudo heterojunction Bipolar Transistors with lateral emitter resistor
    Applied Physics Letters, 1993
    Co-Authors: G B Gao, Z F Fan, N Teraguchi, T C Shen, H Morkoc
    Abstract:

    Both AlxGa1−xAs/AlyGa1−yAs and GaAs pseudo‐heterojunction Bipolar Transistors (HBTs) with lateral emitter resistors (laterally extended emitter ledge) are shown to exhibit base current ideality factors of 1.3 and 1.1, and uniform current gains of 10 and 5, respectively, even at current densities as low as 5×10−11 A/μm2. With this test structure, it is possible to separate the surface effects from the bulk effects. The structures investigated also allowed the confirmation that the emitter edge‐thinning reported recently is very effective for reducing the surface recombination. The structures under investigation also show that GaAs HBTs can operate at collector currents in the microampere range or below.

  • base transit time for sige base heterojunction Bipolar Transistors
    Electronics Letters, 1991
    Co-Authors: G B Gao, H Morkoc
    Abstract:

    The base transit time expressions for SiGe base heterojunction Bipolar Transistors are presented including the accelerating field effects due to the base bandgap grading and doping grading, and the retarding field (opposing drift field) effect from the graded boron profile down towards the emitter. It is found that the retarding field exhibits 40–80% contribution to the base transit time, depending on the boron concentration near the emitter. The results of base transit time from these analytic expressions are unambiguously supported by the published simulation data.