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    carrier mobility of Pmos and Nmos

    What is the relation between carrier mobility (electron and holes) in PN junction with regards to width (W) of Pmos and Nmos for Inverter circuit?

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  2. #2
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    Re: carrier mobility of Pmos and Nmos

    Carrier mobility reduction essentially occurs in strong inversion due to velocity saturation effects, i.e. in short channel devices, so depends much more on the length (L) than on W. See e.g. D. Binkley "Tradeoffs and Optimization in Analog CMOS Design", Chap. 2.4.3. Here's a clipping from the text (p. 16) :

    "A primary effect is velocity saturation associated with the loss of effective carrier mobility caused by a high tangential or horizontal electric field between the pinched-off drain (again, saturation operation is considered) and source."



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  3. #3
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    Re: carrier mobility of Pmos and Nmos

    You should also recognize that you are talking -surface- mobility
    in a MOSFET, which is not the same as bulk carrier mobility in a
    "long" bulk device at all. You have surface scattering and a
    constrained Z dimension.



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