Epitaxial Growth and Stoichiometry Control of Ultrawide Bandgap ZnGa₂O₄ Films by Pulsed Laser Deposition

• Main Authors: Liu Wang, Wenrui Zhang, Ningtao Liu, Tan Zhang, Zilong Wang, Simiao Wu, Zhaolin Zhan, Jichun Ye
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Coatings
• Subjects: ZnGa₂O₄; epitaxial growth; Zn volatilization; pulsed laser deposition; stoichiometry control
• Online Access: https://www.mdpi.com/2079-6412/11/7/782

ZnGa₂O₄ is a promising semiconductor for developing high-performance deep-ultraviolet photodetectors owing to a number of advantageous fundamental characteristics. However, Zn volatilization during the ZnGa₂O₄ growth is a widely recognized problem that seriously degrades the film quality and the device performance. In this study, we report the synthesis of epitaxial ZnGa₂O₄ thin films by pulsed laser deposition using a non-stoichiometric Zn_1+<i>x</i>Ga₂O₄ target. It is found that supplementing excessive Zn concentration from the target is highly effective to stabilize stochiometric ZnGa₂O₄ thin films during the PLD growth. The influence of various growth parameters on the phase formation, crystallinity and surface morphology is systematically investigated. The film growth behavior further impacts the resulting optical absorption and thermal conductivity. The optimized epitaxial ZnGa₂O₄ film exhibits a full width at half maximum value of 0.6 degree for a 120 nm thickness, a surface roughness of 0.223 nm, a band gap of 4.79 eV and a room-temperature thermal conductivity of 40.137 W/(m⋅K). This study provides insights into synthesizing epitaxial ZnGa₂O₄ films for high performance optoelectronic devices.