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Ian T Ferguson - One of the best experts on this subject based on the ideXlab platform.

  • time resolved electroabsorption measurement of the transient Electron Velocity overshoot in gan
    Applied Physics Letters, 2001
    Co-Authors: Michael Wraback, H Shen, J C Carrano, C J Collins, J C Campbell, R D Dupuis, M Schurman, Ian T Ferguson
    Abstract:

    A femtosecond time-resolved electroabsorption technique employing an AlGaN/GaN heterojunction p–i–n diode with a p-type AlGaN window layer and a semitransparent p contact has been used to measure the transient Electron Velocity overshoot in GaN. A peak transient Electron Velocity of 7.25×107 cm/s within the first 200 fs after photoexcitation has been observed at a field of 320 kV/cm. The increase in Electron transit time across the device with increasing field beyond 320 kV/cm provides experimental evidence for a negative differential resistivity region of the steady-state Velocity-field characteristic in this high field range.

  • time resolved electroabsorption measurement of the Electron Velocity field characteristic in gan
    Applied Physics Letters, 2000
    Co-Authors: Michael Wraback, H Shen, J C Carrano, J C Campbell, M Schurman, T Li, Ian T Ferguson
    Abstract:

    A femtosecond optically detected time-of-flight technique that monitors the change in the electroabsorption associated with the transport of photogenerated carriers in a GaN p–i–n diode has been used to determine the room-temperature Electron transit time and steady-state Velocity as a function of electric field. The peak Electron Velocity of 1.9×107 cm/s, corresponding to a transit time of 2.5 ps, is attained at 225 kV/cm. The shape of the Velocity-field characteristic is in qualitative agreement with theoretical predictions.

Siddharth Rajan - One of the best experts on this subject based on the ideXlab platform.

  • density dependent Electron transport and precise modeling of gan high Electron mobility transistors
    Applied Physics Letters, 2015
    Co-Authors: Sanyam Bajaj, Omor Shoron, Jacob B Khurgin, Pil Sung Park, Sriram Krishnamoorthy, Fatih Akyol, Tinghsiang Hung, Shahed Reza, Eduardo M Chumbes, Siddharth Rajan
    Abstract:

    We report on the direct measurement of two-dimensional sheet charge density dependence of Electron transport in AlGaN/GaN high Electron mobility transistors (HEMTs). Pulsed IV measurements established increasing Electron velocities with decreasing sheet charge densities, resulting in saturation Velocity of 1.9 × 107 cm/s at a low sheet charge density of 7.8 × 1011 cm−2. An optical phonon emission-based Electron Velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the Electron Velocity with strong Electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation Velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this re...

  • density dependent Electron transport and precise modeling of gan hemts
    arXiv: Materials Science, 2015
    Co-Authors: Sanyam Bajaj, Omor Shoron, Jacob B Khurgin, Pil Sung Park, Sriram Krishnamoorthy, Fatih Akyol, Tinghsiang Hung, Shahed Reza, Eduardo M Chumbes, Siddharth Rajan
    Abstract:

    We report on the direct measurement of two-dimensional sheet charge density dependence of Electron transport in AlGaN/GaN high Electron mobility transistors. Pulsed IV measurements established increasing Electron velocities with decreasing sheet charge densities, resulting in saturation Velocity of 1.9 x 10^7 cm/s at a low sheet charge density of 7.8 x 10^11 cm-2. A new optical phonon emission-based Electron Velocity model for GaN is also presented. It accommodates stimulated LO phonon emission which clamps the Electron Velocity with strong Electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation Velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  • density dependent Electron transport for accurate modeling of algan gan hemts
    Device Research Conference, 2015
    Co-Authors: Sanyam Bajaj, Omor Shoron, Jacob B Khurgin, Pil Sung Park, Sriram Krishnamoorthy, Fatih Akyol, Tinghsiang Hung, Shahed Reza, Eduardo M Chumbes, Siddharth Rajan
    Abstract:

    We report on accurate modeling of GaN HEMTs for RF operation taking into account sheet charge density (n s ) dependence of Electron Velocity in 2-dimensional Electron gases (2DEGs). Electron Velocity characteristics of the channel directly impact DC and high frequency transistor performance, and it is critical to understand Velocity at all charge density and field conditions to accurately predict large signal performance of GaN HEMTs. Previous models of AlGaN/GaN HEMTs have taken into account field dependence of Electron Velocity, but have not considered its dependence on channel sheet charge density [1]. In this work, we have directly measured Velocity characteristics of 2DEGs as a function of field and sheet charge density, and used them to accurately simulate DC and small signal characteristics of GaN HEMTs. The work done here provides a method to accurately simulate DC and RF characteristics of GaN HEMTs over the entire bias range.

  • Electron Velocity of 6 107 cm s at 300 k in stress engineered inaln gan nano channel high Electron mobility transistors
    Applied Physics Letters, 2015
    Co-Authors: S Arulkumaran, G I Ng, C Manoj M Kumar, K Ranjan, Omor Shoron, Siddharth Rajan, Bin S Dolmanan, S Tripathy
    Abstract:

    A stress engineered three dimensional (3D) Triple T-gate (TT-gate) on lattice matched In0.17Al0.83N/GaN nano-channel (NC) Fin-High-Electron-Mobility Transistor (Fin-HEMT) with significantly enhanced device performance was achieved that is promising for high-speed device applications. The Fin-HEMT with 200-nm effective fin-width (Weff) exhibited a very high IDmax of 3940 mA/mm and a highest gm of 1417 mS/mm. This dramatic increase of ID and gm in the 3D TT-gate In0.17Al0.83N/GaN NC Fin-HEMT translated to an extracted highest Electron Velocity (ve) of 6.0 × 107 cm/s, which is ∼1.89× higher than that of the conventional In0.17Al0.83N/GaN HEMT (3.17 × 107 cm/s). The ve in the conventional III-nitride transistors are typically limited by highly efficient optical-phonon emission. However, the unusually high ve at 300 K in the 3D TT-gate In0.17Al0.83N/GaN NC Fin-HEMT is attributed to the increase of in-plane tensile stress component by SiN passivation in the formed NC which is also verified by micro-photolumines...

Timothy G Wright - One of the best experts on this subject based on the ideXlab platform.

Y Yamaguchi - One of the best experts on this subject based on the ideXlab platform.

  • influence of the Electron Velocity spread and the beam width on the efficiency and mode competition in the high power pulsed gyrotron for 300 ghz band collective thomson scattering diagnostics in the large helical device
    Physics of Plasmas, 2016
    Co-Authors: O Dumbrajs, T Saito, Y Tatematsu, Y Yamaguchi
    Abstract:

    We present results of a theoretical study of influence of the Electron Velocity spread and the radial width on the efficiency and mode competition in a 300-kW, 300-GHz gyrotron operating in the TE22,2 mode. This gyrotron was developed for application to collective Thomson scattering diagnostics in the large helical device and 300-kW level high power single TE22,2 mode oscillation has been demonstrated [Yamaguchi et al., J. Instrum. 10, c10002 (2015)]. Effects of a finite voltage rise time corresponding to the real power supply of this gyrotron are also considered. Simulations tracking eight competing modes show that the Electron Velocity spread and the finite beam width influence not only the efficiency of the gyrotron operation but also the mode competition scenario during the startup phase. A combination of the finite rise time with the Electron Velocity spread or the finite beam width affects the mode competition scenario. The simulation calculation reproduces the experimental observation of high power single mode oscillation of the TE22,2 mode as the design mode. This gives a theoretical basis of the experimentally obtained high power oscillation with the design mode in a real gyrotron and moreover shows a high power oscillation regime of the design mode.

  • influence of the Electron Velocity spread and the beam width on the efficiency and mode competition in the high power pulsed gyrotron for 300 ghz band collective thomson scattering diagnostics in the large helical device
    Physics of Plasmas, 2016
    Co-Authors: O Dumbrajs, T Saito, Y Tatematsu, Y Yamaguchi
    Abstract:

    We present results of a theoretical study of influence of the Electron Velocity spread and the radial width on the efficiency and mode competition in a 300-kW, 300-GHz gyrotron operating in the TE22,2 mode. This gyrotron was developed for application to collective Thomson scattering diagnostics in the large helical device and 300-kW level high power single TE22,2 mode oscillation has been demonstrated [Yamaguchi et al., J. Instrum. 10, c10002 (2015)]. Effects of a finite voltage rise time corresponding to the real power supply of this gyrotron are also considered. Simulations tracking eight competing modes show that the Electron Velocity spread and the finite beam width influence not only the efficiency of the gyrotron operation but also the mode competition scenario during the startup phase. A combination of the finite rise time with the Electron Velocity spread or the finite beam width affects the mode competition scenario. The simulation calculation reproduces the experimental observation of high power...

Jacob B Khurgin - One of the best experts on this subject based on the ideXlab platform.

  • density dependent Electron transport and precise modeling of gan high Electron mobility transistors
    Applied Physics Letters, 2015
    Co-Authors: Sanyam Bajaj, Omor Shoron, Jacob B Khurgin, Pil Sung Park, Sriram Krishnamoorthy, Fatih Akyol, Tinghsiang Hung, Shahed Reza, Eduardo M Chumbes, Siddharth Rajan
    Abstract:

    We report on the direct measurement of two-dimensional sheet charge density dependence of Electron transport in AlGaN/GaN high Electron mobility transistors (HEMTs). Pulsed IV measurements established increasing Electron velocities with decreasing sheet charge densities, resulting in saturation Velocity of 1.9 × 107 cm/s at a low sheet charge density of 7.8 × 1011 cm−2. An optical phonon emission-based Electron Velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the Electron Velocity with strong Electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation Velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this re...

  • density dependent Electron transport and precise modeling of gan hemts
    arXiv: Materials Science, 2015
    Co-Authors: Sanyam Bajaj, Omor Shoron, Jacob B Khurgin, Pil Sung Park, Sriram Krishnamoorthy, Fatih Akyol, Tinghsiang Hung, Shahed Reza, Eduardo M Chumbes, Siddharth Rajan
    Abstract:

    We report on the direct measurement of two-dimensional sheet charge density dependence of Electron transport in AlGaN/GaN high Electron mobility transistors. Pulsed IV measurements established increasing Electron velocities with decreasing sheet charge densities, resulting in saturation Velocity of 1.9 x 10^7 cm/s at a low sheet charge density of 7.8 x 10^11 cm-2. A new optical phonon emission-based Electron Velocity model for GaN is also presented. It accommodates stimulated LO phonon emission which clamps the Electron Velocity with strong Electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation Velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  • density dependent Electron transport for accurate modeling of algan gan hemts
    Device Research Conference, 2015
    Co-Authors: Sanyam Bajaj, Omor Shoron, Jacob B Khurgin, Pil Sung Park, Sriram Krishnamoorthy, Fatih Akyol, Tinghsiang Hung, Shahed Reza, Eduardo M Chumbes, Siddharth Rajan
    Abstract:

    We report on accurate modeling of GaN HEMTs for RF operation taking into account sheet charge density (n s ) dependence of Electron Velocity in 2-dimensional Electron gases (2DEGs). Electron Velocity characteristics of the channel directly impact DC and high frequency transistor performance, and it is critical to understand Velocity at all charge density and field conditions to accurately predict large signal performance of GaN HEMTs. Previous models of AlGaN/GaN HEMTs have taken into account field dependence of Electron Velocity, but have not considered its dependence on channel sheet charge density [1]. In this work, we have directly measured Velocity characteristics of 2DEGs as a function of field and sheet charge density, and used them to accurately simulate DC and small signal characteristics of GaN HEMTs. The work done here provides a method to accurately simulate DC and RF characteristics of GaN HEMTs over the entire bias range.

  • Hot phonon effect on Electron Velocity saturation in GaN: A second look
    Applied Physics Letters, 2007
    Co-Authors: Jacob B Khurgin, Yujie J. Ding, Debdeep Jena
    Abstract:

    A theoretical model is developed for Electron Velocity saturation in high power GaN transistors. It is shown that Electron Velocity at high electric fields is reduced due to heating of Electron gas since the high density of nonequilibrium LO phonons cannot efficiently transfer heat to the lattice. However, the resulting degradation of Electron Velocity is found to be weaker than previously reported. The results are compared with experimental data, and the ways to improve the efficiency of cooling the Electron gas to increase the drift Velocity are discussed.