High-k transition metal oxides in MIS Schottky diodes: Interface and charge transport mechanisms

Transition metal oxide (TMO) interfacial layers in Metal–Insulator–Semiconductor (MIS) Schottky diodes represent a major advancement in optoelectronic device engineering, offering superior performance compared to conventional metal–semiconductor structures. This review systematically evaluates TMOs such as TiO 2 , HfO 2 , ZrO 2 , Ta 2 O 5 , MoO 3 , WO 3 , V 2 O 5 , Y 2 O 3 , and ZnO, focusing on their impact on key diode parameters including barrier height, ideality factor, series resistance, and leakage current. These oxides are selected for their stable interfaces, favorable band alignment, reduced interface state density, high thermal stability, and tunable work functions. Among them, hafnium oxide (HfO 2 ) emerges as the most promising interlayer, delivering higher barrier heights (0.70–1.08 eV) and near-ideal Schottky behavior with ideality factors close to unity (n ≈ 1.0–1.3). These enhancements stem from HfO 2 's high dielectric constant, wide bandgap, low defect density, strong semiconductor compatibility, and suppressed Fermi-level pinning. Electrical characterization using I-V and C-V analyses shows improved rectification, reduced reverse leakage, enhanced breakdown voltage, and excellent thermal stability. Temperature-dependent studies indicate carrier transport dominated by thermionic emission, Poole Frenkel emission, and Schottky emission. Overall, HfO 2 -based MIS diodes are highly suitable for next-generation photodetectors, solar cells, high-power LEDs, and radiation-resistant semiconductor devices due to their superior electrical performance and stable interface quality.