AC transport in short n⁺nn⁺ layers

The admittance of n + nn + semiconductor structures is studied by solving self‐consistently the Poisson equation, the continuity equation, and the linearized Boltzmann equation in the relaxation time approximation for a spatially inhomogeneous electron system. Exact numerical results and an approximate, analytical solution are presented. In addition to the normal bulk admittance and the geometric capacitance of the central n region, the equivalent circuit of the structure consists of contact contributions, the magnitude of which depends on the length of the n region L . At low frequencies the effect of the contacts is to induce a conductance G c , and a capacitance C c , in parallel with G c , in the equivalent circuit. On the other hand, above the plasma frequency of the n region the contact admittance vanishes because of the shunting of the capacitive elements.