Electrical and optical properties of tin-doped CdO films deposited by atmospheric metalorganic chemical vapor deposition

Highly conductive and transparent tin-doped CdO:Sn were deposited via atmospheric metalorganic chemical vapor deposition. Dimethylcadmium (DMCd), tetramethyltin (TMT), and O-2 were used to deposit the CdO:Sn films. The structural, electrical, and optical properties of the fabricated films were influenced by the partial pressures of DMCd and TMT, substrate temperature, film thickness, and annealing conditions. A sheet resistance of 14-17 Omega/sq was obtained for as-deposited CdO:Sn films with a thickness of 120-150 nm. The high conductivity of the films was mainly due to their high carrier concentration (2-3 X 10(21)/cm(3)) and moderate mobility (12-13 cm(2)/V s). The transmission of the films in the visible range was high (80-95%) and shifted towards the blue region due to the Moss-Burstein (M-B) effect. The films exhibited direct and indirect band-to-band transitions, which corresponded to optical bandgaps of similar to3.0 and similar to2.5 eV, respectively. The electro-optical properties of as-deposited CdO:Sn films were further improved by post-deposition annealing. A resistivity value of 1.4-1.6 X 10(-4) Omega cm has been obtained after annealing in He and H-2 ambients, which is the lowest value ever reported for CdO films. (C) 2002 Elsevier Science B.V. All rights reserved.