Patent GB-700241-A (GB)
Title: Semiconductor electric signal translating devices
IPC: H01L29/00
Filed: 1950-04-14
Abstract: 700,241. Nuclear bombardment. WESTERN ELECTRIC CO., Ltd. April 14, 1950 [April 15, 1949; April 27, 1949], No. 9221/50. Class 39(4) [Also in Groups XXXVI and XL(c)] A signal translating device comprises a body of semi-conductive material of one conductivity type having one or more zones of material of opposite conductivity type extending i n t o it. The manufacturing process involved includes the bombardment of N-type material with nuclear particles to produce P- type material, and this may also be used to provide the emitter electrode of a transistor. Fig. 5 shows an embodiment in which a part of a block 30 of N-type germanium is converted to P- type germanium, two wedge shaped or conical shaped portions 31 and 32 being left as N-type germanium. The conversion is effected by bombardment of the N-type material by deuterons, protons or neutrons produced by a cyclotron, or by alpha particles from radioactive sources such as radium, plutonium or polonium. The required shape of the converted material is obtained by directing and controlling the intensity of the bombarding beam and by the use of shields. Ohmic connections, produced for example by rhodium plating, are provided to the P and N portions and to the wedge portions 31 and 32. The device operates as a transistor amplifier, connections 33, 34 and 35 serving as base, emitter, and collector electrodes respectively. The P-type zone is biased negatively with respect to the N-type body. The shape of the P-type zone may be modified, and an accelerating electrode, which serves to reduce transit time effects, may be provided at the end of the P zone opposite to electrode 33. Fig. 14 shows an alternative arrangement, in which two sets of rods of P-type material produced by nuclear bombardment extend from two thin P- type layers into a block of N-type material. This may be used as a diode rectifier or electrodes 333, 334, 335 and 345 may serve as base, emitter, collector and accelerating electrodes respectively. In Fig. 1, the emitter 13 and base 14 electrodes are provided by ohmic connections to a P-type zone 11 which has been produced by nuclear bombardment and an N-type zone respectively, the collector being a point contact situated on the N-type material 10 near the N.P junction. In Fig. 4, a surface layer portion 24 of P-type material which serves as the emitter electrode, is provided on a strip of N-type germanium by a process which comprises electroplating a face of N-type germanium strip with rhodium, shielding the end portions 25 and 26 with gold and bombarding with alpha particles, (which penetrate the rhodium coating) to effect conversion, and then etching and grit blasting with the portions 22, 23 and 24 protected to remove the plating and P-type material from all but the portion 24. Several other embodiments are described, which include features such as having P-type material with portions of different intensity, the conversion of an intermediate layer 18 P-type by control of the energy of the bombarding particles a tapering formation to reduce capacity between electrodes, and a semi-conductor element shaped as a thin disc. The treated elements may be heated to stabilise the newly formed P-type material. Specifications 632,942, 632,980, 700,231 and 700,236, [all in Group XL(c)], are referred to.