Structural insights into nucleation and grain orientation in β-Ga2O3 films grown by MOVPE on off-axis 4H-SiC substrates

In this work, β-Ga2O3 was deposited by low-pressure metal organic vapour phase epitaxy on 4◦ off-axis 4H-SiC. This substrate has a high thermal conductivity and can enable a more effective heat dissipation in vertical power devices compared to the low-conductivity β-Ga2O3 homo-substrates. The obtained heteroepitaxial films were characterized by X-ray diffraction and transmission electron microscopy. Results show that β-Ga2O3 films are composed of grains with three specific in-plane orientations, all characterized by planes of oxygen atoms arranged in a pseudo hexagonal geometry, namely the (-201), which is the main orientation, the (101), which remains confined near the interface, and the two equivalent (310) and (3-10), which instead tend to expand laterally and grow up to the film surface. The interface between β-Ga2O3 and 4H-SiC was thoroughly investigated by electron diffraction and high-resolution scanning transmission electron microscopy. The outcome of this work provides a deeper understanding of the nucleation and growth of β-Ga2O3 on 4◦ off-axis 4H-SiC substrates, focusing on the competition between step-flow and island growth mechanisms.