Effect of substrate orientation on homoepitaxial growth of β -Ga2O3 by halide vapor phase epitaxy

The influence of substrate orientation on homoepitaxial growth of beta-gallium oxide by halide vapor phase epitaxy was investigated. Substrates were cut at various angles Δb from the (001) plane (Δb = 0°) to the (010) plane (Δb = 90°) of bulk crystals grown by the edge-defined film-fed growth method. The growth rate increased with increasing absolute value of Δb near the (001). However, from the (001) to the (010), as Δb increased, the growth rate decreased sharply, and streaky grooves observed in the grown layer on the (001) substrate became triangular pits. The length of the pits decreased with increasing Δb, and a pit-free homoepitaxial layer grew at Δb ≈ 60°. The valley line of the pits was parallel to the [010] direction; therefore, the length of the pits decreased with increasing Δb. In addition, transmission electron microscopy observations of the deepest part of a pit revealed that the pits originate from dislocations propagating in the substrate at an angle of 60° with respect to the (001) plane. Therefore, pits are not formed on the grown layer surface when the Δb of the substrate is ∼60°, because its surface is substantially parallel to the dislocations. The homoepitaxial growth of a pit-free layer on the (011) substrate (Δb = 61.7°) was demonstrated, and void defects and dislocations in the substrate were confirmed by the etch-pit method to not be inherited by the homoepitaxial layer.