Role of Junction Geometry in Determining the Rectification Performance of Nanostructured TiO2-Based p-n Junctions

This paper reports on the influence of junction geometry on the determination of the rectification performance of nanostructured titanium dioxide (TiO₂)-based p-n homojunctions. Two types of p-n junction devices with different junction area/geometry were fabricated. Sol-gel grown undoped TiO₂ nanoparticle layer was employed as the p-type side in both the cases. Electrochemically grown TiO₂ nanotube array was used as the n-type side in one junction, while thermally grown n-TiO₂ thin film was used in another. It was found that, due to unique advantage of excessively large junction area, p-TiO₂/n-TiO₂ nanotube device offered a dramatically improved ideality factor (4) and a rectification factor (1093) compared with its p-TiO₂/n-TiO₂ (thermally grown) counterpart (17 and 34, respectively). The 2-D distribution probability of the depletion region in the case of the first device was empirically correlated with the experimental findings and was supported by the corresponding C-V measurement results.