Open Access Article
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Impact of Growth Method on the Structural and Electronic Properties of Nb:Bi₂WO₆ Thin Films for High-Power pn Junction Applications
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Ichiro Takakuwa , Ryusuke Seino , Seiya Suzuki , Keishi Nishio , Shutaro Asanuma , Yoshihiro Nemoto , Yuki Nishimiya , Yoichi Higashi , Toshimitsu Ito and Makoto Minohara
First published on 14th October 2025
Abstract
Development of high-breakdown voltage power devices requires design of suitable p-type wide-bandgap oxide semiconductors. We investigated the growth of Nb-doped Bi₂WO₆ (Nb:BWO) thin films, which are promising candidate ptype wide-bandgap oxide semiconductors, via pulsed laser deposition (PLD) and solid-phase epitaxy (SPE). While X-ray diffraction analyses confirmed successful growth of the target Nb:BWO phase by both methods, X-ray fluorescence and photoemission spectroscopy revealed the presence of a significant Bi deficiency and defect states near the Fermi level in the PLD-grown film, in contrast to the SPE-grown film. These defects likely degrade device performance, as demonstrated by the poorer rectifying behavior of the Nb:BWO/β-Ga₂O₃ heterojunctions fabricated using the PLD-grown film. By contrast, SPE-grown film showed better stoichiometry and improved electronic properties. These results indicate that SPE is a superior method for growth of high-quality p-type oxide films suitable for power device applications.