Precise control of the microstructural, optical, and electrical properties of ultrathin Ga2O3 film through nanomixing with few atom-thick SiO2 interlayer via plasma enhanced atomic layer deposition

Abstract

Ultrathin Ga₂O₃ films nanomixed with few atom-thick SiO₂ interlayer were deposited on silicon and quartz substrates through plasma-enhanced atomic layer deposition. Upon adjusting the number of SiO₂ atomic layers, different Si doping levels in Ga₂O₃ films were obtained. Herein, we report for the first time the use of this method to investigate the doping effect and realize the precise control of the microstructural, optical, and electrical properties of the Ga₂O₃ films. The experimental results indicated that the microstructural properties such as density, roughness, and chemical composition of the films are all affected by the number of doped SiO₂ atomic layers. As the Si doping concentration increased in the films, the refractive index of the Ga₂O₃ films decreased monotonically, the optical transparency improved, and the average transmittances were >95% from ultraviolet to visual wavelengths for all the Si-doped Ga₂O₃ films. Moreover, the energy band-gap increased with the increase in Si composition, increasing from ∼4.8 eV for the undoped film to ∼5.1 eV for the film with a 20 at% Si doping level. Moreover, the breakdown field of the Ga₂O₃ film linearly improved from 6.8 MV cm⁻¹ to 10.7 MV cm⁻¹ as a function of the Si content. More importantly, this result enlightened us that the breakdown field of the Ga₂O₃ film can be further improved by increasing the Si doping concentration. This study provides a means to expand the properties of the new doped films and develop Ga₂O₃ film-based devices, such as transparent electrodes, photodetectors, thin film transistors, or high-power high-voltage devices.