GB796407A - Method of producing single semiconductor crystals - Google Patents

Abstract

Small single crystals of germanium are formed by heating germanium or germanium dioxide to produce small molten specimens each containing germanium in an amount equal to that desired in a diode or transistor crystal, and cooling the molten specimens at a rate between 0.3 DEG C. and 2000 DEG C. per second to <PICT:0796407/III/1> <PICT:0796407/III/2> <PICT:0796407/III/3> obtain single crystals. In one method specimens 9 (Fig. 1) of germanium or germanium dioxide are placed on a plate 10, which may be of quartz or graphite and may be coated with carbon black, in a quartz tube 13 surrounded by a heating coil 14. The heating coil may be moved longitudinally so that the specimens are melted and then cooled, or the coil may be stationary and the plate 10 moved along the tube 13. A gas such as hydrogen, nitrogen, helium or argon may be passed through the tube 13 by means of an inlet 16 and an outlet 18. The plate 10 may be flat or may have recesses for locating the specimens, or may have grooves narrower than the specimens so that the specimens are supported by the upper edges of the grooves. Junctions may be obtained by adding donor or acceptor inpurities to the specimens, or by heating and cooling the specimens with a vacuum in the tube 13 and then adding impurities by metal evaporation or by admitting gaseous metal compounds. In another method discrete germanium specimens are embedded in a mass of carbon black which is heated and cooled, or a specimen 40 (Fig. 4) is placed in a quartz mould 42 having a cover 43 in a furnace 41, the single crystal being formed as a thin slab as the cover flattens the specimen when it melts. In a further method germanium 58 (Fig. 5) is melted in a chamber 56 having a bore 57 by a heater coil 59 surrounding a quartz tube 50. Drops of molten germanium pass through the bore 57 and form single crystals as they fall, which are received in a liquid bath 51. Gas is passed through the tube 50 by means of inlets 60 and outlet 61 to provide a suitable atmosphere and to delay the descent of the drops.