Low Resistance TiO2/p-Si Heterojunction for Tandem Solar Cells

Niobium-doped titanium dioxide (Ti1-xNbxO2) films were grown onp-type Si substrates at low temperature (170 degrees 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 degrees C in an H(2)atmosphere for 30 min. It was shown that the Ti0.72Nb0.O-28(2)/p(+)-Si heterojunction fabricated on low resistivity silicon (10(-3)omega cm) had linear current-voltage characteristic with a specific contact resistivity as low as 23 m omega center dot cm(2). As the resistance dependence on temperature revealed, the current across the Ti0.72Nb0.28O2/p(+)-Si heterojunction was mainly determined by the band-to-band charge carrier tunneling through the junction.