Improvements in junction type semiconductor electrical devices

摘要

768,731. Semi-conductor devices. GENERAL ELECTRIC CO. Oct. 15, 1954 [Oct. 16, 1953], No. 29773/54. Class 37. A method of making a PN junction device comprises fusing to a surface of a semi-conductor body of one conductivity type a blob of material characteristic of the opposite type to form a PN junction, applying insulating material at least to the surface surrounding the blob and applying pressure to the blob to flatten it out over the insulating material so giving improved heat conductivity between the body and blob. A slice 1 of monocrystalline N type Ge cut from an ingot grown by seed crystal withdrawal from a donor doped melt is soldered to a fernico base 2 by a donor-containing solder 3, e.g. tinarsenic alloy as described in Specification 748,845 in a non-oxidizing or reducing atmosphere. A blob 5 of ductile acceptor, e.g. thallium, aluminium, zinc, but preferably indium, is fused to the opposite face of the body, preferably in a separate heating at 500-600‹ C. The body is then etched electrolytically, or chemically using, e.g. 80 per cent nitric, 15 per cent hydrofluoric, 3 per cent acetic acids mixed with 2 per cent bromine for circa 5-10 seconds to remove the surface portion of the junction and washed. The body is then dipped in an insulating varnish or resin and cured or a solution, e.g. of oleophenolic, epoxymelamine, acrylic, vinyl, polystyrene, polyethylene or phenolformaldehyde resin is sprayed or brushed all over the surface or just around the blob and the blob deformed by pressure to extend over the insulating layer so formed. Alternatively, insulating layers of alumina, silica, germanium oxide or titanium oxide or a sheet of mica or one of the above resins closely fitting around the electrode may be used. Si may be used instead of Ge and the body may alternatively be P type in which case the blob contains donor material, e.g. Sb, P, As. A graphite block 11 (Fig. 5) pressed against the flattened blob 10 by spring 12 may be used with the device to further improve the heat dissipation.