Patent GB-1278644-A (GB)
Title: Solid-state multi-region device
Inventor: DAHLBERG REINHARD
IPC: H01L31/06
Filed: 1969-06-13
Abstract: 1278644 Solid state devices R DAHLBERG 13 June 1969 [22 Jan 1969] 30177/69 Headings H1A and A4D A solid state device comprises an alternating sequence of two types of region having different electrical resistances, one of the regions, region I, of each adjacent pair having a mobile charge carrier concentration of less than 10<SP>19</SP> cm<SP>-3</SP> and the other region, region II, of the pair having a corresponding concentration of greater than 10<SP>19</SP> cm<SP>-3</SP>. Each region is less than 5 x 10<SP>-3</SP> cm thick, and the two I/II interfaces on opposite sides of each type I region exhibit different thermal work functions for carriers within the type I region. There are at least ten individual regions in all. Fig. la shows an example of a sequence of N- and P-type Si layers meeting these requirements and comprising a multi-region rectifier blocking in one direction only. The shaded regions comprise the type II regions. Figs. 1b-1e (not shown) illustrate examples of alternative sequences which comprise similar rectifiers. Various different materials are referred to in the Specification for use in these examples. Fig. 2a shows a Si device including a layer sequence which exhibits blocking properties in both directions. Figs. 2b-2m (not shown) illustrate alternative sequences, with materials referred to for each sequence, having similar properties. The differential work functions on either side of the type I regions may also be achieved by the use of very thin layers of various specified materials through which tunnelling can occur. Various types of device may employ such arrangements, those referred to in the Specification including rectifiers, electronic switches, solar cells, photo-resistors, light-emitting diodes, electronic storage elements, magnetic field-dependent switches or resistors, and piezo-electric or ferro-electric elements. If very thin, < 10<SP>-5</SP> cm, layers of certain amorphous semi-conductors are used for the regions I, application of a high electric field may cause a sudden change to a crystalline phase, with a consequent increase in conductivity, the layers reverting to the amorphous phase in the presence of a current surge or when the applied field drops below a critical strength. Thermo-electric devices may also be made using such arrangements. For example, thermocouples may include legs of the form shown in Figs. la or 2a, or in accordance with Figs. 1d or 2e, 2f, 2h, 2i or 2j (not shown). Fig. 6 shows an alternative arrangement for use as a photo-thermal element. Three Si wafers are cut at 45 degrees to the plane of the various regions and mounted together, enclosed in silicon dioxide 2. Such a device is sensitive to light as well as to heat.  Fig. 7 illustrates a super-conducting device in which the regions I comprise 10<SP>-5</SP> cm thick N-type strontium titanate layers I while the regions II are constituted by layers 2 of Pt and layers 3 of caesium antimonide. The different work functions on either side of each side of each layer 1 produce very high field strengths which, it is stated, give rise to super-conductivity when the device is cooled below the critical temperature. In a further embodiment, Fig. 8 (not shown) a similar device is composed of alternating layers of Ti, vapour deposited titanium dioxide, gold and'sputtered titanium dioxide, and in this case the superconductivity is used in a direction parallel to the planes of the layers. In both embodiments magnetic fields may be applied.