Improvements in or relating to methods of forming p-n junctions in semiconductors

849,549. Semi-conductor devices. GENERAL ELECTRIC CO. Ltd. July 29, 1958 [Aug. 15, 1957], No. 25846/57. Class 37 A PN junction in a semi-conductor body is formed by heating a wire comprising significant impurity in contact with a semi-conductor body to form a molten alloy region and then cooling in a manner such that the region of the body adjacent the molten region cools faster than the portion of the wire adjacent this region. The process avoids discontinuities in the recrystallised region. Fig. 1 shows an interim stage in which an N-type silicon body 1 is supported by a carbon block 2. Initially, an aluminium wire 16 suspended from support 17 is lowered into contact with the body 1 on support 2 which is heated to 700 ‹C. by the passage of electric current. On contact, the current is switched off so that the wire and body alloy together. The body 1 with attached wire 16 is then inverted and placed in block 2 as shown in Fig. 1, the block 2 then being heated to 800 ‹C. for about six seconds. While nitrogen is passed from stem 12 to escape through hole 14. Wires 5 and 6 are associated with a thermo-couple for temperature measurement. The assembly is allowed to cool to form a PN junction, the wire being maintained throughout the cooling at a higher temperature than the body owing to the thermal capacity of the surrounding blocks 2. An ohmic connection to the body 1 is made by heating a gold-antimony wire 18 as it is lowered to contact body 1. The assembly is then etched, washed, mounted on two copper wires 25 and 26 (Figs. 2 and 3) in a copper envelope comprising two cup-shaped portions 20 and 21 which are cold welded together in an atmosphere of nitrogen. A drop of silicone resin is disposed on body 1 and wires 16 and 18. Specification 817,636 is referred to.