Stable Space-Charge Layers Associated with Bulk, Negative Differential Conductivity: Further Analytic Results

The gross features of previous computer results on stable accumulation and depletion layers are explained analytically. Further, the drift velocity of the accumulation plane in the singular limit, D=0, is obtained by a simple geometric construction based solely on the velocity-field characteristic. This result is related to the drift velocity of the finite accumulation layer, at the same outside velocity, for the D≠0 case via a stringent inequality. For the general case, D=D(F), a new integral equation is derived from the starting differential equations.