Chemical solution deposition of a (GaAl)2O3 single layer with high thickness and silver-enhanced crystal quality

Traditional chemical solution deposition (CSD) methods for growing Ga2O3 films face two main issues: limited thickness per deposition, necessitating multiple coating-annealing cycles for adequate film thickness, and a decline in crystal quality with increased thickness. This study introduces an innovative CSD technique for fabricating (GaAl)2O3 films, achieving both high thickness and superior crystal quality, where the aluminum content results from the diffusion of aluminum from sapphire substrates during annealing. The technique uses a precursor solution with high viscosity and cation concentration, allowing single-layer thicknesses of up to 180 nm. Additionally, the incorporation of silver nitrate for silver doping enhances nucleation, growth, and epitaxial quality, inducing a unique twelve-fold symmetry in the (−201) oriented (GaAl)2O3 films. Notably, silver serves as a catalyst and largely evaporates at high temperatures, thus preserving the film's final composition and performance. This study highlights the effectiveness of this CSD approach in simultaneously improving crystal quality and achieving desired film thickness, making it a promising method for mass production of high-quality (GaAl)2O3 films.