Classical semiconductor with no surface states

We consider first the simplest possible case of an interfacial potential similar to that shown in Fig. 4. If a small potential modulation is applied to the semiconductor in depletion, its effect can be calculated by eliminating nx between eqns. (87) and (90) to obtain, for x W 

Similarly, Jj (0) - uLd/W, since most of the contribution to the integral comes in the region where x 0. Inserting these values into eqn. (91), we obtain 

Multiplying eqn. (95) by ia) and inserting this into the expression for j, we find 

Comparing this with eqn. (97), assuming Csc Cb, and writing qs = — kTWje0L%, we have 

Provided that Ls is large compared with VP, Cb may be neglected and we arrive at the very simple equivalent circuit 

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