On the Forward Bias Excess Capacitance at Intimate and Mis Schottky Barrier Diodes With Perfect or Imperfect Ohmic Back Contact

Abstract

An experimental explanation of the forward bias Capacitance;frequency plots for intimate or MIS SBDs with perfect or imperfect ohmic back-contact has been made. It has been shown that there is no excess capacitance that could be ascribed to the interface states or minority carrier at the intimate SBDs (that is, without interfacial layer) with the perfect ohmic back contact (low-resistance). It has been found that the excess capacitance is only measurable at SBDs with imperfect back contacts or with an interfacial layer which separates the interface states from the metal. It has been found that excess capacitance can be generated by varying the resistance or quality of the back-ohmic contact to the bulk semiconductor substrate, that is, the density of minority carriers that are injected by the Schottky contact depends sensitively on the properties of the ohmic back-contact. Again, it has been seen that the excess capacitance has appeared owing to the interface states plus minority carriers in MIS SBDs with imperfect back contacts. Thus, it has been concluded that the excess capacitance at nonideal Schottky contacts has been caused not only by the interface states but also by the minority carriers or by the interface states plus minority carriers due to the poor frontside or poor backside contacts. Thereby it has been experimentally shown that every forward bias C-f-plots with excess capacitance cannot be used to extract the results related to the interface states.