THE SURFACE ACOUSTIC WAVE INDUCED JUNCTION STORAGE CORRELATOR
Abstract
One of the more promising surface acoustic wave (SAW) devices under consideration for use in real-time signal processing systems is the silicon storage (memory) correlator. Several physical configurations and storage mechanisms have been investigated in relation to this device. Among them, the most attractive configurations employ Schottky or pn diode arrays to implement the storage function. The purpose of this document is to report the results of a study of an alternative storage array for use as a SAW storage correlator, an array consisting of induced junctions. The induced junction device is an adaptation of the metal-ZnO-SiO(,2)-Si (MZOS) configuration with an additional aluminum grating at the ZnO-SiO(,2) interface. Charge injection and trapping inside the ZnO layer has been associated with the bias instability of the MZOS SAW devices. With the presence of this grating, the otherwise undesirable charge injection phenomenon can be employed constructively to create a signal storage medium. The observed device characteristics are found to be similar to those of pn diode storage correlator, while providing greater ease of fabrication and opportunities for use in conjunction with semiconductors other than silicon. Fast erasure of a reference signal stored in a SAW correlator for the purpose of replacing it with a new signal is essential to many signal processing applications. Signal storage erasure is used to speed up the relaxation process of the non-equilibrium state created at the silicon surface by the writing process. Both photo-generation of carriers within the depletion region and the lateral motion of minority carriers at the silicon surface could be used to quicken the signal storage decay process. Photo-erasure of the stored signal in a SAW correlator has been demonstrated by using a Schottky diode device. A new method of stored signal erasure, electric erasure, implemented with the induced junction storage correlator is described and demonstrated.
Degree
Ph.D.
Subject Area
Electrical engineering
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