Study of p-type AlN-doped SnO ₂ thin films and its transparent devices

The electrical properties of transparent Al-doped tin oxide (SnO ₂ ), N-doped SnO ₂ , and AlN-doped SnO ₂ thin films were studied. The Al-doped tin oxide (SnO ₂ ) thin films all show n-type conduction regardless the annealing condition. The n-type conduction of the as-deposited N-doped SnO ₂ , and AlN-doped SnO ₂ thin films could be converted to p-type conduction by annealing the films at an elevated temperature of 450°C. XPS analysis verified that the substitution of N ions in the O ion sites in the annealed N-doped SnO ₂ and AlN-doped SnO ₂ thin films were responsible for the n-p conduction transition. The conduction of the annealed N-doped SnO ₂ and AlN-doped SnO ₂ thin films could be converted back to n-type conduction by thermally annealing the films at higher temperature, over 450°C. The p-n conduction transition is related with the outgassing of N ions in the p-type N-doped SnO ₂ and AlN-doped SnO ₂ thin films. Remarkably, we found that the Al content can retard the outgassing of N ions in the p-type N-doped SnO ₂ and AlN-doped SnO ₂ thin films and prolong the p-n conduction transition temperature above 600°C. XPS analysis revealed that the formation of the SnNAl bond improved the stability of the N ions in the AlN-doped SnO ₂ thin films. I-V curve of the p-type AlN-doped SnO ₂ /n-type fluorine-doped SnO ₂ junction exhibited clear p-n junction characteristics, a low leakage current under the revised bias (1.13 × 10 ^-5 A at -5 V), and a low turn-on voltage (3.24 V). p-Type AlN-doped SnO ₂ /n-type fluorine-doped SnO ₂ junction exhibited excellent transmittance (over 90%) in the visible region (470-750 nm).