No abstract

extra diffraction spots reveal they may be due to Pb. Precipitation of Pb can occur in PbSe (4), due to the retrograde nature of the Pb solidus boundary (5). However, in accordance with the PbSe phase diagram near stoichiometry (5, 6) the amount of precipitate should be several orders of magnitude less than that observed here. In order to account for the large volume fraction of second phase observed, either the retrograde solubility is much larger than has been previously reported or the specimen grew nonstoichiometrically. The latter is more plausible since some of the more volatile Se component may have been lost during the growing procedure.The presence of a two-phase structure has important implications for use of this semiconductor in electronic applications. FUrther experiments are in progress to ascertain what growth conditions lead to the observed two-phase structure.

Results of measurements are presented of the Hall coefficient and conductivity in undoped samples of HgTe in the temperature range 4.2 t o 300 K and magnetic fields up to 30 kG. The results are explained using a three-carrier model of conductivity in conduction band states, valence band states, and impurity states. The temperature dependence of the electron concentration and the contribution to the electrical conductivity of "heavy" carriers are determined.Es werden Ergebnisse von Messungen des Hall-Koeffizienten und der Leitfahigkeit in undotierten Proben von HgTe im Temperaturbereich 4,2 bis 300 K und bei magnetischen Feldern bis zu 30 kG mitgeteilt. Diese Ergebnisse werden mit einem Drei-LadungstragerModel1 der Leitfahigkeit in Leitungsbandzustanden, Valenzbandzustanden und Storstellenzustlinden erklart. Die Temperaturabhangigkeit der Elektronenkonzentration und der Beitrag zur elektrischen Leitfahigkeit Ton schweren Ladungstragern werden bestimmt.