George Augustus Castellion

Preparation and Semiconducting Properties of Cd3P2

Single and polycrystalline samples of Cd3P2 have been prepared. Undoped samples are n‐type with carrier concentrations between 1017 and 1018 cm−3. The thermoelectric power of these samples goes up to −170 μV/°C at 300°K. Mobility values up to 3000 cm2/V sec at 300°K were measured. The mobility of single crystals varies in the extrinsic range near room temperature proportionally to T−1.1 (T is temperature). Optical measurements indicate an optical band gap of approximately 0.5 eV. The results of annealing experiments support the assumption that the high electron concentration of undoped samples is due to phosphorus vacancies. The doping properties of various elements have been studied. Copper introduces what is probably a deep‐lying acceptor level, but p‐type samples could not be obtained.

Anomalous Thermal Conductivity of Cd3As2 and the Cd3As2−Zn3As2 Alloys

The room‐temperature lattice thermal conductivity of Zn3As2 is 0.012 W/cm·°C; that of Cd3As2 is 0.014 W/cm·°C or less. Anomalously low thermal conductivities (as much as 30% below calculated values) are found for samples of Cd3As2 and Cd‐rich alloys of Cd3As2 with Zn3As2 where the electrical conductivity is high (>103 Ω−1 cm−1). Thermal conductivities for Cd3As2 samples fall into two groups: Samples doped with an element which is expected to enter the anion sublattice have normal thermal conductivities, while undoped samples or those doped with an element which should enter the cation sublattice tend to have anomalously low thermal conductivities. High electron mobilities and general lack of correlation of carrier concentration with thermal conductivity indicate that the anomaly is not in the electronic component of thermal conductivity. Instead, doping experiments, as well as the temperature dependencies of thermal conductivities indicate that the anomaly is entirely in the lattice component and is due t...