Shoichi Minagawa

Basic characteristics of surface‐acoustic‐wave convolver in monolithic MIS structure

We propose a new nonlinear theory including the gate‐voltage dependence and the effect of surface states based on a simple model (low‐frequency limit) of surface‐acoustic‐wave (SAW) convolver in monolithic MIS structure, and we confirm our theory by experiment on the n‐Si/SiO2/ZnO/Al system. Our results show that the convolution signal corresponds to the derivatives of C‐V curves in the ideal MIS structure and the effect of surface states appears in the peak shift.

Efficient ZnO-SiO 2 -Si Sezawa Wave Convolver

A detailed design theory of the Sezawa wave convolver is developed, and the fabrication of a high-efficiency convolver using a ZnO-Si0,-Si structure is discussed. The important points to improve the efficiency are 1) an optimum choice of SAW propagation direction on the Si substrate, 2) an optimum design of the resistivily of the Si epitaxial layer and ZnO film thickness, and 3) an improvement for low- ering SAW propagation lsos and resistance of output circuit. The ex- periments were carried out for two specifications each with a 20-mm and 40-mm gate length. The highest efficiency (F,) of -35 dBm was obtained in the gate length of 20 mm while the time-bandwidth product (ET) was 107. The highest ET product of 227 was obtained in the gate length of 40 mm, while F, was -47.5 dBm. At the present time, the maximum available ETproduct is less than 320 due to the group velocity dispersion.

A Characteristic of Surface-Acoustic-Wave Convolver in Monolithic MIS Structure

A theory of lossless parametric operation in surface-acoustic-wave convolver is developed by applying the treatment of parametric operation in varactor diodes. It is shown that much improvement in convolver efficiency can be achieved by the separation of the output circuit from the input circuit by filters, by the elimination of useless constant capacitance components by tuning with inductance in input and output circuits, and by the impedance matching in input and output circuits. Preliminary experiments on such a convolver in a ZnO/SiO2/Si system confirm our theory and show the highest internal efficiency among convolvers examined so far.

Propagation loss of surface acoustic waves on a monolithic metal‐insulator‐semiconductor structure

A theory for the propagation loss of surface acoustic waves on a monolithic metal‐insulator‐semiconductor structure is developed. We derive the theory for the case where an epitaxial layer of semiconductor on a heavily doped substrate is used. The experimental results obtained by using Sezawa waves on a monolithic ZnO/SiO2/Si structure are compared with the theoretical predictions. The theoretical values are in good agreement with the experimental values in regard to the bias‐voltage characteristics, the temperature characteristics, and the effects of the impurity concentration and the thickness of the epitaxial layer. It is shown that the surface‐acoustic‐wave propagation loss is considerably sensitive not only to the impurity concentration but also to the thickness of the epitaxial layer.

SAW Convolver Utilizing Sezawa Wave in a Monolithic ZnO/Si Configuration

The optimum design for the monolithic Sezawa wave ZnO/Si convolvers is clarified on crystal cuts and SAW propagation directions in silicon. Theoretical analysis was carried out using an equivalent transmission line circuit model of SAW. The calculated bilinear convolution characteristics well agree with the experimental results. The terminal convolution efficiency FT=-47.5 dBm was obtained in the [001] direction on (110) Si. Dynamic range over 80 dB was observed in the [011] direction on (100) Si. The temperature and dc gate bias stability characteristics are described.