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Samples of TlBiTe2 and TlTe were prepared and characterized by x-ray powder diffraction, differential thermal analysis, scanning-electron-microscope and electron-microprobe studies, and transport measurements.The two materials were found to be distinctly different with regard to melting point, crystal structure, temperature dependence of the resistivity and Hall coefficient, and sign of the Hall coefficient and thermoelectric power. The Hall mobilities (in cm /V aec) are -84 and +3 at 300 K and -128 and+1120 at 4.2 K for T1BiTet and TlTe, respectively. The temperature dependence of these mobilities, combined with the apparently large carrier densities, suggests that TlBiTe2 is a highly degenerate n-type semiconductor, while TlTe is more likely to be a semimetal. Discontinuities in the resistivity and Hall-coefficient data of TlTe at 170 K suggest the occurrence of a phase change at that temperature.The two sets of results were compared with data on material which had been described by Hein and Swiggard as TlBiTe2, a new nonmetallic superconductor.But the normal-state properties of a portion of this material closely resemble those of T1Te, not TlBiTe2. A search for superconductivity in further samples of both compounds is needed to clarify this situation.

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Schottky-barrier photodiodes were prepared by depositing either lead or indium onto p-type PbSxSe1−x epitaxial films. These photodiodes had 77 °K zero-bias resistance-area products of 26–21 000 Ω cm2 as x varied from 0 to 1, respectively. The peak detectivities were close to the background limit and could be composition tuned between 3.7 and 6.9 μm at 77 °K. Narrowband detectors were prepared by using one film as a short-wavelength cutoff filter and a second film, of slightly different composition, as the detector. These devices exhibit high quantum efficiencies, low half-bandwidths, and insensitivity to variations in incident angle.