A high-frequency bidirectional capacitance method to study the evolution of the interface state density generated at low temperatures

A high-frequency bidirectional capacitance method has been modified to study the evolution of the density of interface states generated by Fowler-Nordheim tunneling injection. The interface state response during the measurement of the capacitance curves in both directions has been analyzed in detail in order to extend the use of the method to intermediate temperatures. In this way an analytical approximation of the occupation factor through stepwise functions has been obtained, following the evolution of the sample from inversion to accumulation. It has been confirmed that Fowler-Nordheim injection at 77 K does not immediately generate interface states, even in the absence of an intermediate state of positive charge trapping, and that thermal activation is necessary for such states to be produced.