Comprehensive charge transport and interface-state analysis of Au/Al2O3/n-Si Schottky diodes via multi-technique electrical characterization

In this study, an Al2O3 interfacial layer was fabricated on n-type Si substrates via a sol–gel route and integrated into Au/ Al2O3/n-Si/Al Schottky diodes. The structural, morphological, and electrical properties of the Al2O3 thin film and their influence on charge transport and interface-state dynamics were investigated. X-ray diffraction (XRD) revealed the coexistence of dominant α- Al2O3 and transition alumina phases, indicating partial phase transformation and structural disorder. FE-SEM and EDS confirmed a uniform, dense morphology with homogeneous elemental distribution; however, combined with XRD results, these findings suggest nanoscale inhomogeneities, including phase boundaries and crystallographic defects. Electrical characterization was performed using I–V, C–V, and G–V measurements. The diode exhibited strong rectification with a barrier height of ≈0.85 eV and an ideality factor of ≈2.30, indicating non-ideal transport dominated by interface states and the Al2O3 interfacial layer. Charge transport behavior evolves from ohmic-like conduction to SCLC-like and trap-influenced transport regimes. Under reverse bias, the low-field transport behavior is found to be more consistent with Schottky-emission-like conduction, while trap-assisted processes become increasingly significant at higher electric fields. The interface state density (Nss), evaluated using Hill–Coleman and high–low frequency methods, was on the order of 1012 eV−1cm−2 with strong energy and frequency dependence. Frequency-dependent C-2–V analysis showed that donor concentration, barrier height, and depletion width are influenced by interface states and interfacial polarization. Overall, the structural and electrical results reveal a physically consistent qualitative relationship between sol–gel-derived microstructural features and the observed non-ideal device characteristics.