Effects of Interface States on the Characteristics of MOS Transistors

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Abstract
The presence of fast interface states gives rise to a reduction of the number of mobile carriers in inversion layer and, therefore, has effects on various characteristics of MOS transistors. In order to obtain quantitative information on these effects, numerical computations of the characteristics are carried out, as examples, for the cases that the density distribution of the interface states is expressed as N t (E t )=N t0δ(E t -E t0); N t (E t )=N·exp [-{(E t -E t0)/σ}2] and N_t(E_t)=N·exp [-{(E_t-E_t0)/σ}^2] for E_t>E_t0, =N for E_t≤E_t0, and the results are plotted for different N t0, N, E t0 and σ. It is pointed out that the mobility obtained in a conventional manner, for example, from the slope of the straight line of the g D vs V G ' curve at V D =0 might be not real but only “seeming” due to the influence of the interface states near the band edge.