Crystal growing process

摘要

In pulling a dentritic crystal from a supercooled melt using a seed crystal having two or more interior twin planes and orientated as shown in Fig. 2, a seed crystal with its tip premelted is contacted with a pre-supercooled melt. A single dendritic crystal is thereby produced as an axial extension of the seed crystal. Materials specified are germanium, silicon, Group III-Group V compounds, and Group II-Group VI compounds. Semi-conductor materials may be intrinsic or doped (n- or p-type). The melt may be supercooled 1 DEG -40 DEG C. Pulling may be effected in an atmosphere of argon, helium, hydrogen, or nitrogen. The pulling rate may be 6,25-62,5 cm./min. The premelting may be effected by the passage of a gas discharge between the seed and the melt. Direct or alternating current may be employed. In the former case, the seed may be the anode or cathode. The distance between the seed and melt during discharge may be 1/8 inch. The current may be 1-10 milliamperes and the voltage 300-1000 volts. As shown in Fig. 1, a gas discharge is formed between a seed 26 (as anode) in an electrically conducting holder 28 and a melt 18 (as cathode) in a graphite crucible 16, the holder 28 and crucible 16 being connected by a circuit comprising bush contact 54, direct current power source 44, impedance member 48, switch 50, and crucible support 14. The impedance member may be a vacuum tube triode with plate and grid connected together to form a diode. Specification 913,674 is referred to.