Methods of manufacturing selenium rectifiers

摘要

809,080. Selenium rectifiers. LICENTIA PATENT-VERWALTUNGS G.m.b.H. Feb. 7, 1956 [Feb. 7, 1955], No. 3816/56. Drawings to Specification. Class 37. A method of making a selenium rectifier comprises the following steps : (i) applying to a metal carrier plate a layer of Cd or Cd alloy with a melting-point higher than 220‹ C.; (ii) heating the Cd or alloy layer to 100-140‹ C., applying to it a Se layer poor in halogen (e.g. less than 1013 atoms/cc.) and forming the layer at between 205‹ C. and its melting-point; (iii) applying a second Se layer relatively rich in halogen (e.g. more than 1016 atoms/cc.) and forming it at 130-200‹ C.; and (iv) applying an electrode to the second Se layer in such a way as to avoid the formation of a barrier layer. The first Se layer which after forming is of high resistivity, is preferably applied by evaporation so that its thickness may be kept to a minimum. The carrier plate may be of Al, Ni or Ni-plated Fe and preferred Cd alloys are a Bi : Cd alloy containing less than 40 per cent by weight of Bi, a Sn : Cd alloy containing less than 40 per cent of Sn, and a Pb : Cd alloy containing less than 82.5 per cent Pb. Thallium and/or indium in free or combined form may be added to the Cd or alloy in amounts between 0.1 and 0.001 per cent. The further electrode may be formed by applying an evaporated bismuth selenide layer to the second Se layer and the spraying on a layer of Bi. Alternatively Bi may be sprayed on the second Se layer before it is formed.