Fabrication of p-type ZnO thin films via magnetron sputtering and phosphorus diffusion

ZnO thin films were deposited on heavily phosphorus-doped (n+-Si) substrates by radio frequency magnetron sputtering. The films were changed from n-type to p-type by phosphorus diffusion from the n+-Si substrates to the ZnO films and being activated thermally during deposition. n-Type ZnO (n-ZnO) films were also deposited onto the p-type ZnO (p-ZnO) films to form n-ZnO/p-ZnO/n+-Si multilayer structures. The cross section of the multilayer structure was examined by scanning electron microscopy. Crystal structures of the p-ZnO films were studied by X-ray diffraction and were confirmed to be highly c-axis oriented primarily perpendicular to the substrate. Photoluminescence spectra of the p-ZnO films showed that band-edge UV emission predominated. The hole concentration of the p-ZnO films was between +1.78×1018 cm−3 and +1.34×1019 cm−3, and the hole mobility was 13.1–6.08 cm2/V s measured by Hall effect experiment. The formation of p-ZnO films was confirmed by the rectifying characteristics of the p-ZnO/n+-Si heterojunctions and the n-ZnO/p-ZnO homojunction on the multilayer structure as well as by the experimental results of Hall effect.