DEVELOPMENT OF TECHNIQUES FOR PREPARING HOMOGENEOUS SINGLE CRYSTALS OF LEAD TELLURIDE, LEAD SELENIDE, AND LEAD SULFIDE

Abstract : Research results showed that vacuum sublimation can yield PbTe with high apparent electron mobilities. However, examination of the crystals revealed the presence of a second (Pb-rich) phase, and results of electrical- property studies suggest that the high mobilities may be due to the presence of the second phase. Results of studies of the doping of PbTe with Hg and Pt, although not conclusive with regard to Hg, indicated that Pt is a donor in PbTe that appears to react with intrinsic defects in such a way that free-carrier concentrations and carrier scattering are reduced. High-mobility Pt-doped crystals were prepared with 77K carrier concentrations as low as 5 x 10 to the 16th power/cu cm. Several techniques, including growth from the melt, vapor growth, solution growth, and heat treatment, were investigated for the preparation of low-carrier-density crystals of PbTe-SnTe alloy. The better crystals, with carrier concentrations in the 10 to the 16th and 10 to the 17th powers/cu cm, ranges were prepared by vapor growth. Although large crystals of PbTe and PbTe-SnTe alloy were grown from solution, further development of the method is required.