Modeling of charge transfer by surface acoustic waves in a monolithic metal/ZnO/SiO2/Si system

This paper discusses modeling of minority-carrier charge transfer by surface acoustic waves (SAW´s). An idealized, structure independent model which includes the mechanism of carrier diffusion is described and definitions of charge-transfer efficiency and charge capacity analogous to those of a conventional charge-coupled device are introduced and developed. The model is used to predict the fundamental upper limit performance of the device in the absence of surface-state trapping and bulk recombination generation. The parameters of the model are evaluated for the monolithic metal/ZnO/SiO2/Si system, and the model is used to predict charge distributions and charge capacity for surface wave frequencies in the range of 40 MHz to 2 GHz. At high frequencies, the predicted device performance is found to be limited by carrier diffusion and the SiO2thickness.