Substrate-dependent thermal modulation of electrical and dielectric properties in p-MoO₃/n-semiconductor Heterojunctions

Abstract

Controlling interface characteristics in metal-oxide-semiconductor heterojunctions is crucial for advancing next-generation electronic and optoelectronic devices. In this work, a detailed study on the characteristics of p-MoO3 heterostructures prepared on four different n-type substrates having wide bandgaps (Si, InP, GaAs, and SiC) before and after annealing at 200 °C in ambient air conditions was carried out. The deposition of p-MoO3 resulted in the formation of orthorhombic α-phase with polycrystalline nature. Annealing caused a significant transformation at the p-MoO₃/n-SiC interface, but this transformation altered the transport mechanism rather than improving classical diode performance. Changes in barrier height and rectification ratio indicate a reshaping of the interface chemistry and carrier transport mechanism. This transition is characterized by an increase in series resistance (Rs ~ 3.68 × 10⁷ Ω), a decrease in barrier height from 1.531 to 1.203 eV, and a rectification ratio of 2.12. Also, the annealing process leads to noticeable changes in the electrical characteristics of the p-MoO₃/n-GaAs heterojunction, suggesting possible modifications at the heterointerface. These changes may be associated with thermally induced variations in the interfacial defect distribution, stoichiometry, and interface properties. The frequency dependent dielectric studies on the p-MoO3/n-SiC heterostructure indicated non-Debye dielectric relaxation and strong interfacial polarization with hopping dominated ac conductivity. The results described above outline a substrate-dependent annealing approach that is crucial for developing MoO3 devices for power electronic and optoelectronic applications.