The Heteroepitaxy of Thick β-Ga(2)O(3) Film on Sapphire Substrate with a β-(Al(x)Ga(1−x))(2)O(3) Intermediate Buffer Layer

A high aluminum (Al) content β-(Al(x)Ga(1−x))(2)O(3) film was synthesized on c-plane sapphire substrate using the gallium (Ga) diffusion method. The obtained β-(Al(x)Ga(1−x))(2)O(3) film had an average thickness of 750 nm and a surface roughness of 2.10 nm. Secondary ion mass spectrometry results indicated the homogenous distribution of Al components in the film. The Al compositions in the β-(Al(x)Ga(1−x))(2)O(3) film, as estimated by X-ray diffraction, were close to those estimated by X-ray photoelectron spectroscopy, at ~62% and ~61.5%, respectively. The bandgap of the β-(Al(x)Ga(1−x))(2)O(3) film, extracted from the O 1s core-level spectra, was approximately 6.0 ± 0.1 eV. After synthesizing the β-(Al(x)Ga(1−x))(2)O(3) film, a thick β-Ga(2)O(3) film was further deposited on sapphire substrate using carbothermal reduction and halide vapor phase epitaxy. The β-Ga(2)O(3) thick film, grown on a sapphire substrate with a β-(Al(x)Ga(1−x))(2)O(3) buffer layer, exhibited improved crystal orientation along the (-201) plane. Moreover, the scanning electron microscopy revealed that the surface quality of the β-Ga(2)O(3) thick film on sapphire substrate with a β-(Al(x)Ga(1−x))(2)O(3) intermediate buffer layer was significantly improved, with an obvious transition from grain island-like morphology to 2D continuous growth, and a reduction in surface roughness to less than 10 nm.