F23294-CanadaABSTRACT OF THE DISCLOSUREA radiation detector made of hyperpure germaniumhas generally the shape of a follow cylinder with an outergenerally cylindrical surface and an inner generally cylin-drical surface and is formed with a p+ contact and n+ contact.One of the contacts is on the outer cylindrical surface ofthe semiconductor and the other is on the inner cylindricalsurface, and both contacts are themselves cylindrical. Eachcylinder formed by a contact is open at at least one end thereof,the open ends being adjacent rather than opposite ends of therespective cylinders. One of the contacts is a thin contact,having a thickness of one micron or less. The germanium crystalis formed with an annular groove coaxial with the contacts andextending to within one millimeter of the thin contact at aposition inward of the open end of the thin contact. Thus,when a reverse bias is applied across the germanium crystalbetween the contacts, the resulting equipotential lines arerelatively crowded at the groove, the electric field is ofreduced strength adjacent the open end of the thin contact,and reverse leakage current is inhibited.
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