Dispositifs amplificateurs utilisant des semi-conducteurs ou des cristaux

737,579. Semi-conductor devices. STANDARD TELEPHONES & CABLES, Ltd. Oct. 9, 1953 [Oct. 15, 1952], No. 25844/52. Drawings to Specification. Class 37. In a method of making a rectifier comprising a cats-whisker in contact with a germanium crystal, a surface film of an alloy of tin or lead with germanium is produced by an electroforming process. In one embodiment a layer of tin or lead oxide (preferably Pb3O4) is stuck to the surface by an organic binder, e.g. nitrocellulose, and a series of current pulses passed through the cats-whisker into the germanium dissociates the oxide and alloys the released metal with the germanium surface, while in the other embodiment the cats whisker is coated with a layer of pure tin or lead which is injected into the germanium surface by the electroforming current. Such a lead coating may be produced on the whisker by electrodeposition from a sulphamate electrolyte. A cats-whisker of tungsten is preferred and the oxide layer or tin or lead coatings must be free of significant impurities. The effect of this surface alloying is to decrease the forward resistance and thereby improve the rectification ratio.