CHARGE TRANSFER BY SURFACE ACOUSTIC WAVES IN A MONOLITHIC ZINC-OXIDE ON SILICON SYSTEM
Abstract
Modelling and experimental verification of minority carrier charge transfer by surface acoustic waves are described. The mathematical model which is developed is designed to be valid at high frequencies where carrier diffusion is an important factor. The analysis leads to the conclusion that, by appropriately including diffusion effects, the presence of diffusion prohibits the perfect synchronous transport of charge in the potential wells produced by the surface acoustic wave. While it is possible to transfer most of the charge synchronously, there must be a small but finite loss of charge from the well due to the finite mobility of the minority carriers. Definitions for charge capacity and charge transfer efficiency are developed. Model parameters are evaluated for the monolithic Metal/ZnO/SiO(,2)/Si system and device performance as a function of surface wave frequency and power is predicted. Experiments pertaining to the transfer of charge by surface acoustic waves are also described, and a discussion of the factors involved in the design and fabrication of such a device is included. Observation of minority carrier transport in the monolithic device is then reported. Operation of the device was achieved using optical generation of signal charge as well as injection by means of a p-n junction. Less than ideal device performance such as excessive time delay, charge spreading and low charge capacity are explained in terms of high sensitivity to surface state traps. Lateral bias effects and charge loading of the surface wave are also described.
Degree
Ph.D.
Subject Area
Electrical engineering|Energy
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