GROWTH AND IR-TRANSMISSION OF SB-DOPED POLYCRYSTALLINE GERMANIUM

Antimony-doped polycrystalline germanium ingots have been grown by a directional solidification method using graphite crucibles. Antimony-germanium alloys have been prepared by melting the desired amount of high purity antimony (99.9%) metal with high purity germanium (50-OMEGA cm, p-type) and subsequent directional solidification. Antimony dopant having 0.007-OMEGA cm resistivity and type n has been used to grow n-type polycrystalline germanium ingots from 50-OMEGA cm, p-type polycrystalline germanium charge. Infrared transmission of Sb-doped polycrystalline germanium has been measured and it has been found that Sb-doping enhances the IR-transmission. Undoped high purity 50-OMEGA cm, p-type germanium (6 mm thick) showing 0.12-0.20 transmission in the 5-15-mu-m wavelength range has been doped with antimony and directionally solidified. The Sb-doped large grain (2-5 mm) polycrystalline germanium grown by the above method shows enhanced IR-transmission in the 5-10-mu-m wavelength range and it is quite uniform (0.35 +/- 0.02).