Patent GB-874657-A (GB)
Title: Improvements in or relating to methods and devices for producing plasma oscillationsin electronic semi-conductor bodies
IPC: H03B9/12
Filed: 1957-08-30
Abstract: 874,657. Semi-conductor circuits. SIEMENS & HALSKE A.G. Aug. 30, 1957 [Aug. 30,1956], No. 27448/57. Class 40(6) [Also in Group XXXVI] Plasma oscillations are produced in a semiconductor body of such shape and material that 1/3(#no<SP>2</SP>+#po<SP>2</SP>) - 1/32(γn<SP>2</SP>+γp)<SP>2</SP> - γnγp) O, an output circuit being provided to extract oscillations at Langmuirs natural plasma frequency of the body. # no  and # po  represent the plasma frequency as a function of the impurity concentrations, no and po, of donors and acceptors respectively; #n and #p denote the friction constants i.e. collision frequencies of electrons and holes respectively. The plasma oscillations may be produced by applying a short pulse containing the plasma frequency or by providing drift effect by applying a direct or alternating electric field above or below the Zener breakdown level or thermal gradient through the semi-conductor body. The theoretical aspect is discussed. Fig. 1 shows a semi-conductor body 1 having ohmic end electrodes 2 and 3 and resonant circuits 6 and 7 tuned to the plasma frequency. A current pulse to input circuit 6 produces plasma oscillations in body 1 which drift towards output circuit 7 due to the electric field produced by a voltage applied between electrodes 2 and 3. Feedback between circuits 7 and 6 may be arranged to provide an oscillator, and an additional amplifier may be provided in the feedback path. Modulation may be effected, for example by providing an emitter electrode, the injected carriers modifying the plasma frequency. Capacitative or inductive coupling may be used, and ohmic electrodes 2 and 3 may be replaced by capacitative or rectifying electrodes, the latter consisting of point contacts or PN junctions. More than one input or output circuit may be provided, and coupling may be provided by means of a hollow tube surrounding the semi-conductor body; two input frequencies having a sum or difference frequency equal to the plasma frequency may be applied. Fig. 5 shows a transistor arrangement with base zone 14, emitter 15 and collector 16 and ohmic end electrodes 17 and 18 to produce a drift effect. A hollow tube 19 surrounding the base zone 14 is used to produce oscillations at plasma frequency in the body which are used to modify the normal transistor operation. A plurality of emitters and/or collectors may be provided. The device may be used as a wave filter, Lecher line, timing or delay element, the analogue of a travelling wave tube or as a modified Hall device. The semi-conductor body may be hollow, annular, cylindrical, spherical, forked or cross or egg shaped and have zones of differing impurity concentration, basic material or conductivity type whereby standing waves may be produced, and it may have differing surface states. The semi-conductor material preferably has high carrier mobility and may consist of A 3  B 5 , A 2  B 6  or A 1  B 7  compounds with flourspar or antifluorspar lattice. A magnetic field may be associated with the device. A plurality of these devices may be interconnected to provide a line and column assembly in association with an electron beam for connecting or injecting. The output may be applied to storage or calculating devices. The device may be operated at a very high or very low temperature.