Growth and Characterization of n-Type Hexagonal Ta2O5:W Films on Sapphire Substrates by MOCVD

Abstract

Tantalum oxide is a wide bandgap material commonly used as an insulating dielectric layer for devices. In this work, hexagonal Ta2O5 (δ-Ta2O5) films doped with tungsten (W) were deposited on α-Al2O3 (0001) by metal–organic chemical vapor deposition (MOCVD). The effects of W doping on the structural, morphology, and photoelectrical properties of the obtained films were studied. The results showed that all W-doped films were n-type semiconductors. The XRD measurement result exhibited that the increase in the W doping concentration leads to the changes in the preferred growth crystal plane of the films from δ-Ta2O5 ((Formula presented.)) to (0001). The 1.5% W-doped film possessed the best crystal quality and conductivity. The Hall measurement showed that the minimum resistivity of the film was 2.68 × 104 Ω∙cm, and the maximum carrier concentration was 7.39 × 1014 cm3. With the increase in the W concentration, the surface roughness of the film increases, while the optical bandgap decreases. The optical band gap of the 1.5% W-doped film was 3.92 eV. The W doping mechanisms were discussed.