COATINGS FOR P-I-N BEVELED-EDGE DIODES

1,211,733. Semi-conductor devices. BROWN BOVERI & CO. Ltd. 30 Nov., 1967 [2 Dec., 1966], No. 54544/67. Heading H1K. A PIN device having a bevelled edge 3 is provided with a surface layer 9 on the bevelled edge of the same conductivity type as the narrow-end region 6. The doping concentration in the layer 9 is arranged so that the surface density n R of charge carriers in the layer 9 is substantially equal to n F cosα, where α is the bevel angle and n F in the surface density of charge carriers occuring at the interfaces of the I region with the P and N type end regions 6, 7 under conditions of maximum attainable reverse voltage across the device. In the embodiment a 1000#cm. Si body is provided with P and N type end regions 6, 7 by diffusion of boron and phosphorus respectively, and a bevelled edge 3 is formed ultrasonically. A boron-doped P type layer 9 is epitaxially deposited on the edge 3 and is protected by a coating 10 of varnish or oxide. The layer 9 may alternatively be formed by diffusion or ion-bombardment. A Mo carrier 8 is soldered to the Si body, a further electrode is provded on the end region 6, and the arrangement is provided with a housing.