Nicholas P. Sepelak

KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
  • May 10, 2022 // 4:50pm

    4.3 Transfer of the AFRL 0.14 μm AlGaN/GaN-on-SiC MMIC Process to MACOM’s Commercial Fab

    G. Cueva, MACOM
    E. Werner, KBR, Wright-Patterson AFB
    A. Islam, Air Force Research Laboratory
    N. Miller, Air Force Research Laboratory
    A. Crespo, Air Force Research Laboratory, Sensors Directorate
    Nicholas P. Sepelak, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    D. Walker Jr., Air Force Research Laboratory
    Gary Hughes, Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH
    R. Fitch, Air Force Research Laboratory
    K. Chabak, Air Force Research Laboratory, Sensors Directorate
    Andrew Green, Air Force Research Laboratory, Sensors Directorate
    Kyle Liddy, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
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  • May 11, 2022 // 11:40am

    8.3 Device Figure of Merit Performance of Scaled Gamma-Gate β-Ga2O3 MOSFETs

    Kyle Liddy, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Ahmad Islam, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Jeremiah Williams, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Dennis Walker, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Neil Moser A., Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH,
    Kelson Chabak, Air Force Research Laboratory, Sensors Directorate
    Andrew Green, Air Force Research Laboratory, Sensors Directorate
    Daniel M. Dryden, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Nicholas P. Sepelak, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
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  • 7.3.2023 Scaled ?-Ga2O3 MOSFETs with Pulsed Laser Deposition-Regrown Ohmics

    Daniel M. Dryden, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Hyung Min Jeon, KBR Inc.,
    Kyle Liddy, Air Force Research Laboratory
    Ahmad Islam, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Dennis E. Walker Jr., Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH,
    Jeremiah C. Williams, Air Force Research Laboratory, Sensors Directorate
    Nicholas P. Sepelak, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Nolan S. Hendricks, Air Force Research Laboratory, Sensors Directorate
    Kevin Leedy, Air Force Research Laboratory, Sensors Directorate
    Kelson Chabak, Air Force Research Laboratory, Sensors Directorate
    Andrew J. Green, Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH,

    7.3.2023 CSMantechExtendedAbstract4

  • 12.2.2023 High Temperature Studies of 140 nm T-gate AlGaN/GaN HEMT Devices

    Ahmad Islam, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Adam Miesle, KBR Inc.
    Nicholas P. Sepelak, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Hanwool Lee, KBR Inc.
    Dennis E. Walker Jr., Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH,
    N. Miller, Air Force Research Laboratory
    Matt Grupen, Air Force Research Laboratory, Sensors Directorate
    Kyle Liddy, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    Antonio Crespo, Air Force Research Laboratory, Sensors Directorate
    Gary Hughes, Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH
    Wenjuan Zhu, University of Illinois, Urbana
    Kelson Chabak, Air Force Research Laboratory, Sensors Directorate
    Andrew J. Green, Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH,

    12.2.2023_CSMANTECH_FinalPaper_HT_Islam_rev

  • 4A.2 – Temperature Effects on DC and RF Characteristics of 140 nm AlGaN/GaN HEMTs with Regrown Contacts

    B. K. Sarker, KBR, Inc.
    Nicholas P. Sepelak, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    D.E. Walker Jr. , Sensor Electronic Technology
    K. Nishimura, KBR, Air Force Research Laboratory Sensors Directorate, WPAFB, OH, USA
    A. Crespo, Air Force Research Laboratory, Sensors Directorate
    Gary Hughes, Air Force Research Laboratory, Sensors Directorate, Wright-Patterson AFB, OH
    A.J. Green
    A. Islam, Air Force Research Laboratory

    4A.2 Final.2025

    Abstract
    We conducted DC and small-signal RF characterization on AlGaN/GaN high-electron-mobility transistors (HEMTs) over a range of temperatures to examine temperature-dependent variations in key device performance metrics including transconductance (gm), extrinsic cutoff frequency (fT), maximum gain frequency (fmax), unilateral power gain (UPG), and maximum stable gain (MSG). Our findings indicate that device parameters decline with increasing temperature at a distinct rate. Specifically, a 100°C rise results in fT and fmax dropping by about 8 GHz and 17 GHz, respectively, while MSG decreases by approximately 1 dB. These changes are inherent to the device physics and are not influenced by its geometry or operational mode.