MECHANISMS FOR THE OPERATION OF THIN-FILM TRANSISTORS ON FERROELECTRICS

The electric field emanating from the surface of a poled ferroelectric can control the conduction properties of an overlying semiconducting film; this combination of materials can thus serve as a non-destructiv e readout, non-volatile memory device. Here we will describe a variety of experimental studies of these devices designed to probe the physic s of their operation. The experimental systems included sputtered, n-t ype semiconductor (SC) films of In2O3 and ZnO deposited on bulk PLZT f erroelectrics (FE) and thin PZT FE films. Two distinctly different typ es of device response were measured in this study; in the first, the c hange in SC film conductance observed in the remanent FE state is in t he direction expected from the remanent polarization vector in the fer roelectric. In the second, typically seen in thin film FE devices, the opposite behavior is observed. We find that these two general cases o f behavior, including the observed variations of the SC film conductan ces and carrier mobilities, can be described by a general model which takes into account not only the FE displacement vector, but also charg e injected from the semiconductor into the ferroelectric during biasin g of the gate.