GB1070194A - Improvements in and relating to electrical delay lines - Google Patents

Abstract

1,070,194. Semi-conductor devices. SOCIETE D'ELECTRONIQUE ET D'AUTOMATISME. May 20, 1964 [June 5, 1963], No. 20774/64. Heading H1K. [Also in Division H3] A delay line comprises a body of monocrystalline semi-conductive and piezo-electric material having at or adjacent opposite ends two regions acting as electrical-to-mechanical and mechanical-to-electrical transducers respectively, with D.C. bias sources connected between the ends and a non-rectifying contact at the centre of the intermediate portion of the body, which is of opposite conductivity type to the end regions. The material may be hexagonal zinc or cadmium sulphide, cubic zinc sulphide, or an A III B v compound such as gallium arsenide or phosphide, rendered P or N conducting by doping e.g. with zinc, cadmium, germanium or tellurium. The transducing regions are formed by establishing PN junctions in the material (e.g. by diffusion, deposition or alloying), which when polarized by external batteries produce regions of high resistance. Thus in Fig. 2 junctions are formed at 12 and 13 by diffusing zinc or a zinc-gold alloy into N-type gallium arsenide and an ohmic contact made at 6 by a localized silver-tellurium alloy. The junctions are biased in the directions shown by batteries 7, 8 and a signal source 9 joined in series with one of the batteries. The alternating field in the space-charge zone 14 produces an alternating elastic stress in the material which is propagated down the material as a longitudinal mechanical wave to the similar space-charge region 15 at the far end. Here the wave generates an electric signal which is detected or utilizedat 10. No reflection occurs if the resonant frequency of the region is the same as that of the signal, this frequency being controlled by the D.C. bias. If the regions are located on top of the material instead of at the ends the mechanical wave will be transverse (Fig. 4, not shown). The material should be cut so that the crystallographic axes are suitable for the mode to be propagated. The delay time depends on the distance between the space-charge regions and this can be altered by varying the thickness of the regions with the applied bias. Reference has been directed by the Comptroller to Specification 1,015,559.