Heteroepitaxial growth of β-Ga2O3 thin films on c-plane sapphire substrates with β-(AlxGa1-x)2O3 intermediate buffer layer by mist-CVD method

Abstract

As a new-type of ultra-wide bandgap semiconductor, β-Ga2O3 has received widespread attention due to its great potential applications in high-power devices and deep ultraviolet photodetectors. However, the conventional material epitaxial growth methods (such as MBE, MOCVD and HVPE) are always based on the expensive vacuum equipment and time-consuming. In this work, a low-cost and non-vacuum mist-CVD method is used to grow β-Ga2O3 films heteroepitaxially on sapphire substrates. In order to improve the quality of β-Ga2O3 films, the β-(AlxGa1-x)2O3 is first grown on sapphire substrate and used as the intermediate buffer layer to epitaxially grow β-Ga2O3 film, which can decrease the lattice mismatch and improve the β-Ga2O3 quality. A series of characterization techniques are used to characterize the properties of samples. The results of XPS and UV-Vis tests show that the aluminum composition of β-(AlxGa1-x)2O3 films grown at 850 °C and 900 °C are 0.24 and 0.43, respectively, and the corresponding band gap is 5.36 eV and 5.55 eV respectively. After using β-(AlxGa1-x)2O3 as the intermediate buffer layer, the FWHM of β-Ga2O3 film is 1.131°, the RMS roughness is 3.04 nm, and it has an ideal band gap (4.91 eV), which demonstrates the obvious improvement compared to the sample without the intermediate buffer layer. This shows that β-(AlxGa1-x)2O3 as an intermediate buffer layer can significantly improve the quality of heteroepitaxially grown β-Ga2O3 films.