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Author Topic: Is there a fundamental physical limit for the On/Off ratio of a transistor?  (Read 4212 times)

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Offline weixiang

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Is there a fundamental physical limit for the On/Off ratio of a transistor?
« on: May 3, 2019, 17:57 »
Dear QuantumATK experts,
I would like to know if there exists a physical limit for the transistor On/Off ratio in terms of the channel material energy band gap.
For example, Si has a band gap of 1.14 eV and it may have some kind of limits on the maximum On/Off ratio in the form of exp(Eg/KT)?
I am not sure about this relation exists or not because I don't have a strong background in physics, but I would like to justify my result from the calculation.

Thanks!
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Offline weixiang

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Re: Is there a fundamental physical limit for the On/Off ratio of a transistor?
« Reply #1 on: May 8, 2019, 16:28 »
Can anyone answer my question? many thanks!
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Offline atkfonda

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Re: Is there a fundamental physical limit for the On/Off ratio of a transistor?
« Reply #2 on: May 12, 2019, 11:00 »
May I say, that the limit of ON/OFF is infinite ?

In principle, the off current can be as small as close to zero, which makes ON/OFF approach infinite.

For example, in graphene (as in the figure), which has a zero gap, ON/OFF ratio can be described as
(V_ON / V_OFF)^2, when V_OFF is near the Dirac point, which has zero electronic density of states.
Then it is reasonable to have a large ON/OFF ratio. Right?

Please comment.
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