Patent GB-814896-A (GB)
Title: Improvements in semi-conductor devices
IPC: H01L29/00
Filed: 1955-09-23
Abstract: 814,896. Semi-conductor devices. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 23, 1955 [Sept. 27, 1954], No. 27184/55. Class 37. [Also in Group XL (c)] A transistor device comprises a first zone of one conductivity type having one face covered by an ohmic contact to maintain the zone at a substantially uniform potential, lying adjacent a second zone of opposite conductivity type which bears an ohmic contact and an electroformed point collector contact. The device, as shown in Fig. 2, comprises a germanium or silicon body having a thin P-type region 3, one surface of which is covered with an ohmic contact layer 7, and an N-type region 2 bearing point contact emitter electrode 8, electroformed point contact collector electrode 9 and two spaced ohmic electrodes 5 and 6 which can act as base electrodes and provide a potential gradient along zone 2. Operation of the device utilizes the current amplification or inherent alpha of the point contact collector. Zone 3 may be 0.1 mil. thick and the thickness of zone 2 must be less than the diffusion length, e.g. 0.9 mil. Various uses of the device are described. Fig. 2 shows an arrangement in which input signals applied to emitter 8 appear in amplified form in the collector 9 circuit, the collector characteristics being controllable according to the potential of zone 3 which is governed by electrode 7. The potentials of electrodes 5 and 6 are adjusted so that part of junction 4 is forward biased and part reverse biased, the relative proportion being varied according to the potential of electrode 7. Fig. 4 shows an embodiment in which electrodes 8 and 6 are omitted; electrode 5 is earthed and a negative bias is applied to collector 9. Input signals are applied to electrode 7 via an isolating capacitor 22 so that P-zone 3 acts as the emitter and amplified signals appear in the collector circuit output terminals 21 and 20. It is alleged that automatic biasing of the emitter (i.e. zone 3) occurs rendering any external bias source unnecessary. In a modification of Fig. 4 capacitor 22 is replaced by a resistor, and it is alleged that the arrangement then constitutes a pulse lengthener. Negative input pulses applied to terminal 24, provided they are of sufficient amplitude to extend beyond cut-off point in respect of current across PN-junction 4, result in longer pulses appearing in the collector circuit. The effect is said to be due to changing of the " transition region " of the PN-junction. In a further modification of the Fig. 4 circuits, there are no connections to electrode 7 and the presence of light or heat on the body region is detected by the appearance of increased collector current. Fig. 7 shows a bistable circuit arrangement in which electrode 5 is positively biased, collector electrode 9 is slightly negatively biased and electrode 7 is earthed. It is stated that the application of a negative pulse to electrode 5, or to collector 9, results in the emission of holes from P region 3 causing the collector current to increase to a stable high current condition. Restoration to the low current condition may be effected by reducing the negative bias on the collector. Cooling of the device may be effected by mounting the semi-conductor body on a heat-conducting plate or rod. In an alternative arrangement, electrodes 5 and 6 are both of annular shape surrounding a central point contact collector electrode; additional electrodes may also be provided for control purposes. Specifications 694,021 and 700,231 are referred to.