Theoretical analysis of PbTe molecular flow in hot wall epitaxy system has been made using a Monte-Carlo approach for free molecular flow. Variation in transmission probabilities with the dimensions of the wall have been obtained. These results are applied to get epitaxial growth conditions for PbTe on KCI substrates. It has been observed that at condensation energy Ec = 1.6 eV, the substrate temperature range obtained using the present analysis agrees well with the experimental observations.
Zinc phosphide thin films were prepared by the hot wall epitaxy technique. The transport properties of films grown at different substrate temperatures from 200 to 350 °C were studied from room temperature up to 600 °C. Films were also grown in pure oxygen and nitrogen atmospheres at a pressure of 10−6 Torr, and the conductivity of the films was measured in situ. Thermoelectric measurements on films grown on mica were also done at various temperatures ranging from 300 to 800 K. Arrhenius plots of electrical conductivity yielded an electronic band gap of 1.32 eV and acceptor levels of 0.21 and 0.49 eV corresponding to interstitial phosphorus and absorbed oxygen levels, respectively. Variation of growth temperature, pressure, and nature of the gas present inside the chamber during growth are shown to result in a range of electrical resistivities and to be responsible for changes in carrier concentration. The sign of Seebeck coefficient was found to change from positive to negative at a temperature of 240 °C for a film grown on mica at a substrate temperature of 350 °C.
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