RF magnetron sputtering of [formula omitted] thin films: Analysis of thermal annealing induced tuning of structural, optical characteristics, and energy band alignments

Abstract

This correspondence showcases the deposition of ultra-wide bandgap β−Ga2O3 thin films via the utilization of RF magnetron sputtering at an elevated deposition temperature of 400 °C, followed by a comprehensive analysis of their structural, surface and optical properties using X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Raman, Ultraviolet–Visible Spectroscopy (UV–Vis), and Atomic Force Microscopy (AFM) at 800 °C, 900 °C, and 1000 °C annealed sample. Annealing up to 1000 °C led to a significant enhancement in the film’s crystallinity by 10%, accompanied by a remarkable decrease in dislocation density of up to 93.5%. The study also observed several key trends upon annealing, including a decreasing lattice constant from 12 to 11.97 Å, and an increase in the bandgap from 4.8 to 5.3 eV. Concurrently, crystallite size was consistently increased from 4.07 to 15.77 nm. The conduction band offset (CBO) decreased with higher annealing temperatures. Additionally, the increase in bandgap led to an enhancement in the critical electric field from 8.9 to 11.2 MV/cm. The Electron Density Mapping (EDM) results depicted a covalent bond between the atoms for different annealing processes along with the fundamental structural change in atomic coordinates and unit cell parameters, which has not been reported yet. These findings underline the remarkable material properties of β−Ga2O3 at 1000 °C temperatures. This establishes it as a compelling substitute for materials like SiC and GaN, showcasing its potential across various high-power applications due to a superior Baliga figure of merit and robust sensitivity even under elevated temperatures, positioning it as a promising candidate for optoelectronic applications.