Two-dimensional analysis of ion-implanted, bipolar-compatible, long- and short-channel junction field-effect transistors

A two-dimensional analysis of ion-implanted, bipolar-compatible, long- and short-channel JFETs is presented. The two-dimensional device simulator PISCES is used to study the steady-state characteristics. The linear and saturation regions are analyzed, and insight about the transition region between them is obtained. Short-channel JFET behavior deviates considerably from the conventional theory developed based on the gradual channel approximation, because the x-direction electric field in the channel of the short-channel JFET is much stronger than that in the long-channel JFET. The study shows that the short-channel JFET has several properties that were not previously emphasized: (a) no pinch-off in saturation operation: (b) free-carrier drift velocity saturates in saturation operation: and (c) power-law I-V characteristics in the cutoff region. Details regarding the shape of the conducting channel, the electric field vectors, the current vectors, and the current-voltage characteristics are provided.>