DETERMINATION OF UNDOPED CDTE(111) SURFACE POLARITY BY SURFACE PHOTOVOLTAGE SPECTROSCOPY

Surface photovoltage spectroscopy has been used as a clear, simple met hod to identify the two polar faces [(111) and (111BAR)] of undoped Cd Te. The difference in electronic structure of the two faces is clearly observed in air on polished untreated samples. The (111BAR)Te surface is characterized by an acceptor level, at an energy 1.17 eV below the conduction-band minimum, which is assumed to result from TeO2-CdTe in teraction. The (111)Cd surface is distinguished by two additional dono r levels, at 1.11 and 1.33 eV above the valence-band maximum, which se em to be due to Cd surface atom displacements, accompanying the Te oxi dation. These assignments are supported by the results obtained after various chemical treatments.