Low Resistance TiO/p-Si Heterojunction for Tandem Solar Cells.

Niobium-doped titanium dioxide (TiNbO) films were grown on -type Si substrates at low temperature (170 °C) using an atomic layer deposition technique. The as-deposited films were amorphous and showed low electrical conductivity. The films became electrically well-conducting and crystallized into the an anatase structure upon reductive post-deposition annealing at 600 °C in an H atmosphere for 30 min. It was shown that the TiNb.O/-Si heterojunction fabricated on low resistivity silicon (10 Ω cm) had linear current-voltage characteristic with a specific contact resistivity as low as 23 mΩ·cm. As the resistance dependence on temperature revealed, the current across the TiNbO/-Si heterojunction was mainly determined by the band-to-band charge carrier tunneling through the junction.