Structural, electrical and optical properties of samarium fluoride doped SnO2 transparent conducting oxide thin films for optoelectronic device applications

Abstract

In this study, p-type transparent tin oxide (SnO2) based semiconductor thin films were deposited onto glass substrates by sol-gel dip-coating method using samarium-trifluoride (SmF3) as acceptor dopant. The films were prepared by co-doping 2 mol.% of SmF3 into SnO2 (SFTO), followed by annealing temperature at 475 °C. XRD analysis results showed that the films exhibited the tetragonal rutile SnO2 phase. The p-type conductance of the SFTO films were confimed by Hall effect and Seebeck coefficient measurements. Resistivity and mobility of the SmF3 doped SnO2 film is 7.83 × 10–3Wcm and 7.57 cm2 V–1 s–1, respectively, which reduce in comparing with those of un-doped SnO2 film. Carrier concentration is large increase from –9.34 ´ 1018 cm–3 for un-doped- to +1.05 × 1020 cm–3  for SmF3 doped-SnO2 film. The p-type SFTO film showed a high transmittance of 74.3% at 550 nm, with band gap energy of 3.63 eV. Furthermore, a transparent p-SnO2:SmF3/n-ZnO:Al (Al doping level of 2 mol.%) heterojunction was fabricated on alkali-free glass substrates. The I-V curve measurement for the p-n heterojunction diode showed a typical rectifying characteristic with a forward turn-on voltage of 1.55 V. With obtained properties, the p-type SFTO film holds great promise for optoelectronic devices applications.