Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs

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Science Advances  02 Sep 2016:
Vol. 2, no. 9, e1601240
DOI: 10.1126/sciadv.1601240

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  • RE:

    A variety of technologies exist for radio frequency (RF) electronics, including GaAs high-electron-mobility transistors (pHEMTs), GaN HEMTs, GaAs heterojunction bipolar transistors (HBTs), and SiGe HBTs. Each technology has its own advantages and limitations, and each is best suited for a unique set of applications. GaAs pHEMTs were chosen as the RF technology to best benchmark carbon nanotube (CNT) field effect transistors (FETs) for the following two reasons. i) similar bandgap: the CNTs in this study have an electrical bandgap ranging from 0.7 to 0.94 eV, which is roughly comparable to that of the channel material of GaAs pHEMTs, which is InxGa1-xAs where x is typically < 0.3, with a bandgap in the range of 1.0 – 1.4 eV.(1) In contrast, GaN has a much larger bandgap of 3.4 eV.(1) ii) Similar application: It is anticipated that CNT FETs will be best suited for low-power, low-noise amplifier applications, which means they will be competing with GaAs pHEMT as an incumbent technology.(2) In contrast, GaN HEMTs are best suited for high-power as opposed to low-power applications due to GaN having a slower electron drift velocity at low electric fields compared to GaAs.(3)

    The effects of radiation on the robustness of the CNT FETs were not studied in this work.

    1. S. Voinigescu, High-Frequency Integrated Circuits. (Cambrdge University Press, 2013).
    2. Private communication with Carbonics Inc. who are commercializing the CNT FET technology for microwave...

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    Competing Interests: None declared.
  • RE: Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs
    • George Chakko, Technology reviewer, Former U.N. correspondent, now retiree

    While acknowledging the obvious merit of the authors’ research, one is in doubt on the cumulative claim, I quote. “CNT array FETs are specifically expected to lead to at least a two- to fivefold gain in the energy-delay product of logic devices (8, 10) (thereby enabling faster switching and lower power consumption) while allowing for particularly high-speed RF amplifier devices with excellent linearity (9) (thereby enabling increased data throughput and lower power consumption). These advances in single CNT FETs and the projected characteristics of array FETs have made it clear that CNTs are prime candidates for next-generation semiconductor electronics that promise substantial performance gains.” (The highlights are mine).
    What I question principally is why the authors did not find it appropriate to research into to compare the CNT devices’ performance as against GaN devices that outclass GaAs devices for sure, although the yield quality price for the GaN is enormously high. Why? I would appreciate if the authors would respond.
    Secondly, what about the radiation immunity grade of these CNT devices for space and military applications?

    George Chakko, Vienna (Austria)
    03/09/2016 23:56 hrs

    Competing Interests: None declared.

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