Selective Doping of Piezoelectric Crystals by Ion Implantation.

摘要

The feasibility of creating n-type conducting regions in semi-insulating (> 10to the 7th power cm) piezoelectric crystals by ion implantation has been investigated. The ultimate purpose would be to form monolithic acoustic surface-wave amplifiers. Experimental studies have been performed with ZnO,CdS,and GaAs. Cadmium sulfide was implanted with B,Al,Ga,Fl,and Cl. Sulfur implantations into GaAs produced n-type layers with mobilities of 2000sq cm/V-sec. Studies of implantation doping with protons into ZnO showed that layers of controlled sheet resistivities could not be predicted but could be produced. Adsorption and desorption of oxygen during and after implantation played a significant role in determining the conductivity of the implanted layer,suggesting that considerable difficulty with stability in the final device might be expected. Carrier mobilities in the proton implanted layers as high as 71sq cm/V-sec were observed,which is sufficient for amplifier action. The monolithic amplifier device has been analyzed theoretically,treating separately the propagating characteristics of surface waves and the amplifying section utilizing a thin doped conducting region. Calculations on the performance of the amplifying element have been made in two ways. First,an analytical expression is derived in a simple way on the assumption that the conducting region is very thin. Second,an exact computer program was developed to describe the operation of a very general amplifying structure. (Author)