Improvements in and relating to semiconductor devices

摘要

1,105,314. Semi-conductor devices. MULLARD Ltd. 19 Nov., 1964 [23 Dec., 1963], No. 50672/63. Heading H1K. A semi-conductor device contains a junction between a region of a single or mixed crystal AIIIBV compound and a region of a manganese arsenide having a composition in the range Mn 1 . 9 As to Mn 2 . 3 As. During the formation of the junction it is possible that one or more very thin intermediate layers of further compounds (e.g. Mn 3 As 2 ) or of material having different electrical properties or different crystalline structure may be formed between the two regions. Such layers if present have a total maximum thickness of the order of 1 Á. Junctions may be made having the characteristics of PN, PP, or NN junctions. They are incorporated in devices such as high-speed switching diodes, tunnel diodes, or especially in photo diodes and in opto-electronic transistors in which they form the collector-base junction. Each of the three embodiments specifically described is a photo-cell. In the embodiment of Fig. 1 a tellurium-doped wafer 1 of gallium arsenide is placed in a carbon jig and has a pellet containing 80% bismuth (as a carrier material) and 20% manganese prewetted to one face at 450‹ C. Two pellets containing 54% bismuth, 44% tin, and 20% platinum are prewetted at 450‹ C. to the opposite face. The pellets are alloyed for 1 hour at 500‹ C. in an evacuated silicon tube and then cooled over a period of 4 hours. A resolidified region 4 consists of bismuth with a little manganese and gallium and constitutes an ohmic contact to a recrystallized region 3 containing manganese arsenide. Ohmic contact is made to the gallium arsenide wafer by resolidified regions 6 (which contain the original elements and a little gallium arsenide) and their underlying recrystallized regions 5 which contain gallium arsenide, bismuth, tin, and lead. Platinum wires are soldered to the contacts. The device is then lightly etched with 30% solution of bromine in methanol, and encapsulated. The manufacture of the second embodiment is generally similar. Here the material alloyed to form the heterojunction consists of a pellet containing 75% bismuth, 10% manganese, and 15% indium arsenide which is prewetted to the body together with a chip of manganese sufficient to make the manganese content of the material alloyed up to 25%. The resolidified region after alloying contains bismuth, indium arsenide, and gallium, and overlies a doped region of manganese arsenide. The third embodiment is generally similar to the second but has all contacts on the same surface. In this case no additional manganese is added to the pellet alloyed to form the heterojunction. In the specific embodiments the heterojunction is formed on a (100) face of gallium arsenide. With the conditions given it is found that there is a lattice mismatch of less than 5% between the (100) plane of gallium arsenide and the (001) plane of the manganese arsenide. Electrical parameters of the three diodes are given including for one of them values of the breakdown voltage at room temperature and at liquid nitrogen temperature. Junctions may also be formed by vapour deposition of manganese arsenide on an AIIIBV substrate or vice versa. Other alloying methods are outlined including some in which the region of AIIIBV material is formed on a manganese arsenide substrate.