Field-dependent mobility model for two-dimensional numerical analysis of MOSFET's

A field-dependent mobility model for use in two-dimensional numerical analysis of MOSFET's is proposed. This model takes into account two field components: One is the gate field which induces carriers in the inversion layer and the other is the drain field which transports carriers to the drain. Mobility is assumed to be a product of two functions, each of which includes only a field component perpendicular or parallel to the current flow (
E_{\perp} or E_{\parallel}
), that is \micro = \micro_{0} f (N_{B}, E_{\parallel})g(E_{\perp}), with
\micro_{0}
and N
B
being a constant and the impurity concentration, respectively. This equation is applied to calculate the mobility at each mesh point in the numerical analysis. The validity of the present model is demonstrated using several MOSFET structures, for example, conventional structures with short and long gate lengths, and offset-gate structrues with channel-doped layers. Reasonable agreement is found between calculated and experimental results under moderate bias conditions. Flat-band voltage, V
FB
, is assumed to be the only fitting parameter and is adjusted once for each set of samples. Quantitative agreement for short-channel MOSFET's is improved, typically by a factor of 2, and errors are within 20 percent with respect to the experiments.