Effect of Sb doping on structural, electrical and optical properties of epitaxial SnO2 films grown on r-cut sapphire

Antimony-doped tin oxide (SnO2:Sb) films have been epitaxially grown on r-cut sapphire substrates by metalorganic chemical vapor deposition (MOCVD). Although the films were all (1 0 1) oriented with rutile structure, they showed different microstructure, electrical and optical properties as Sb doping varied from 0% to 7%. The doping of Sb could reduce the formation of (1 0 1) twins in SnO2 films. The SnO2:Sb film with the lowest resistivity of 1.3 × 10−3 Ω cm and the highest carrier concentration of 2.5 × 1020 cm−3 was obtained at 5% Sb-doping. The undoped and Sb-doped SnO2 films exhibited different electrical transport mechanism. The samples showed high transparency of ∼80% in the visible range. As Sb concentration increased, the absorption edge of the films shifted to shorter wavelength and the calculated optical band gaps were about 3.77-4.11 eV.