Abstract: Method of providing a thinned layer of epitaxial semiconductor material having a substantially uniform reverse breakdown voltage characteristic (RVBV) on a substrate, wherein stringent control is necessary in the determination of the thickness of the epitaxial layer. This method has particular application to the fabrication of high performance Read-IMPATT diodes of gallium arsenide where it is desirable to achieve a device structure in which substantially equal reverse breakdown voltage values exist across the entire substrate. A particular GaAs Read-IMPATT diode has two epitaxial layers including a relatively lightly doped first epitaxial layer disposed on the substrate and a second top epitaxial layer whose thickness must be controlled as to uniformity and as to magnitude to enable proper microwave operation of the device.

Abstract: An electropolished, copper plated, beryllium copper wire is plated with a composite coating of a nickel-iron-cobalt alloy. Such coating consists of a layer having a high anisotropic field parameter, of the order of 6 oersteds or higher, adjacent the surface of the wire, superimposed by a layer having a lower anisotropic field parameter, of the order of 4 oersteds or less. The wire is plated in two plating cells, the first of which is provided with a plurality of passages directing the flow of a plating electrode with a major component of flow across the wire and a minor component of flow in one direction along the wire. The second plating cell is provided with a plurality of passages directing the flow of a plating electrolyte substantially transverse to the wire. The electrolyte supplied to the first cell contains salts of iron, nickel and cobalt, with cobalt being present in a relatively high concentration.