X-ray photoelectron spectroscopy and spectroscopic ellipsometry analysis of the p-NiO/n-Si heterostructure system grown by pulsed laser deposition

We report on the optical properties and the electronic structure of the p-NiO/n-Si heterostructure system, established for optoelectronic applications in the UV spectral region. Pulsed laser deposition was used to deposit p-NiO onto n-Si to form the p-NiO/n-Si heterojunction system. The optical constants (n, k) and the morphological properties were obtained by using a spectroscopic ellipsometry performed in the energy range of 1-5 eV, while the band-offset measurements of the p-NiO/n-Si heterostructure were performed using X-ray photoelectron spectroscopy analysis. Our results show valence and conduction band offsets values between NiO and Si of about 0.34 ± 0.2 eV and 1.68 ± 0.2 eV, respectively. Valence and conduction band offset values assume that a type I band alignment is formed at the p-NiO/n-Si interface, with the conduction band offset being higher than valence band offset. Based on these findings, an energy-band diagram of the heterojunction is constructed to predict the charge transport properties of the p-NiO/n-Si system. We infer that photogenerated holes should experience a lower potential barrier for their transfer across the p-NiO/n-Si interface than photoelectrons, which should experience a larger barrier. Our results pave the way towards the development of these p-NiO/n-Si heterojunctions for UV detectors, solar cells, and self-biased device applications.