**Reinaldo Vega**
@
on

junction abruptness and quantization questions

When setting up the device structure in nanoMOS, the program asks for the source/drain gaussian profile abruptness in units of dec/nm. There are two problems here. First, there’s a typo: the source/drain profile that results shows up in nm/dec, not dec/nm. Second, gaussian profiles do not have constant abruptness. Is it an actual gaussian profile, or is this another typo and the profile is really just a log-linear profile? If it is an actual gaussian profile, then in what part of the profile is the junction abruptness defined? Is it as simple as the distance from the peak where the concentration drops by one decade, or are you using some other metric?

My other question regards the quantum ballistic transport model, which also accounts for, among other things, direct source-to-drain tunneling by solving the schrodinger equation in the transport direction. Does this only model tunneling along the transport direction, or is this schrodinger equation also being applied to solve for quantization within the off-state potential barrier along the transport direction? In other words, if I have a very small gate length, say 3 nm, for NMOS there should be significant hole quantization in the valence band of the off-state barrier along the transport direction, which would change the off-state barrier height. Any input would be appreciated…

thanks, Reinaldo

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Yang Liu@ onI am only shooting the part of the question on the Gaussian doping since Kurtis has given answers to the other part.

I think the profile of Gaussian doping is a true Gaussian, which can be seen from the subroutine in doping.m regarding the Gaussian.

First is how the decay/lens is defined. Take the doping in the source as an example, the Gaussian doping means that the doping in the source is constant as specified as (N_sd-N_body); right at the source/channel junction and to the channel, the doping begins to take a Gaussian profile as N_sd*exp(-((iii_col-junction_l)*dx/decay_lens)

^{2), and this is only for the Gaussian doping from source. If the drain doping is also Gaussian typed doping, add that to the total doping. You can see from the expression that it is a true Gaussian function typically defined as f(x)=N0*exp(-x}2/(2*sigma^2)), except that in the code here decay_lens^{2 is equal to 2*sigma}2. The parameter decay_lens is defined as (1/sqrt(log(10))*dopslope_s), meaning that the doping drops to 1/10 of N_sd when x=decay_lens to the right of source/channel junction.Reply Report abuse

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