The influence of O2 and N2 on the hall and field effect mobilities in CdSe and PbTe thin films

Thin films of CdSe and PbTe were evaporated onto SiO in a vacuum system in which a pressure of less than 5 × 10⁻¹⁰ torr was available. The Hall and field effect measurements were made directly after producing the sample. Furthermore, these measurements were repeated under various partial pressures of O₂ and N₂ up to nearly 10⁺² torr. A remarkable influence of these gases on the mobilities was observed. One can understand this effect by considering that p-type regions are formed at the surface of the n-type semiconductors and thus a diminution of the measured mobilities occurs.