Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences

COLLEGE OF ENGINEERING

UC Berkeley

Fundamental Conductance ÷ Voltage Limit in Low Voltage Tunnel Switches

Sapan Agarwal and Eli Yablonovitch

EECS Department
University of California, Berkeley
Technical Report No. UCB/EECS-2013-247
December 31, 2013

http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-247.pdf

There is a fundamental conductance ÷ voltage limit in low voltage (less than 4kT/q) tunnel switching devices that obtain a sharp turn off by relying upon the band edges to abruptly cut off the available density of states. The Fermi occupation probabilities are thermally broadened by 4kbT. However, current is only allowed to flow in a narrow energy range limited by the applied voltage, V. This means that if we apply a voltage less than 4kbT/q, the conductance will be reduced by at least qV/4kbT. Even with a perfect tunneling probability of 1 in a perfect quantum channel, the conductance quantum would be diminished by qV/4kT. Attempts at lowering the operating voltage below 4kT/q must come at the expense of smaller conductance.


BibTeX citation:

@techreport{Agarwal:EECS-2013-247,
    Author = {Agarwal, Sapan and Yablonovitch, Eli},
    Title = {Fundamental Conductance ÷ Voltage Limit in Low Voltage Tunnel Switches},
    Institution = {EECS Department, University of California, Berkeley},
    Year = {2013},
    Month = {Dec},
    URL = {http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-247.html},
    Number = {UCB/EECS-2013-247},
    Abstract = {There is a fundamental conductance ÷ voltage limit in low voltage (less than 4kT/q) tunnel switching devices that obtain a sharp turn off by relying upon the band edges to abruptly cut off the available density of states. The Fermi occupation probabilities are thermally broadened by 4kbT. However, current is only allowed to flow in a narrow energy range limited by the applied voltage, V. This means that if we apply a voltage less than 4kbT/q, the conductance will be reduced by at least qV/4kbT. Even with a perfect tunneling probability of 1 in a perfect quantum channel, the conductance quantum would be diminished by qV/4kT. Attempts at lowering the operating voltage below 4kT/q must come at the expense of smaller conductance.}
}

EndNote citation:

%0 Report
%A Agarwal, Sapan
%A Yablonovitch, Eli
%T Fundamental Conductance ÷ Voltage Limit in Low Voltage Tunnel Switches
%I EECS Department, University of California, Berkeley
%D 2013
%8 December 31
%@ UCB/EECS-2013-247
%U http://www.eecs.berkeley.edu/Pubs/TechRpts/2013/EECS-2013-247.html
%F Agarwal:EECS-2013-247