Photoelectrochemical etching of ultra-wide bandgap β-Ga₂O₃ semiconductor in phosphoric acid and its optoelectronic device application

The etching process of an ultra-wide bandgap β-Ga₂O₃ semiconductor is challenging, owing to its high chemical robustness and bond strength. We demonstrated the photoelectrochemical (PEC) etching of β-Ga₂O₃ using phosphoric acid as electrical potential and temperature were varied, both of which were proportional to the etching rate. Once initiated at defect sites, the etch pit anisotropically proceeded along the [0 0 1] direction with an activation energy of 46.3 kJ/mol, which is much lower than previously reported values. The PEC etching rate was as high as 0.7 μm/min in the [0 0 1] direction at a bias of 20 V and temperature of 160 °C. The new facet exposed by PEC etching in phosphoric acid was found to be (−2 0 1), which is assumed to be stable because the Ga-terminated (−2 0 1) surface is converted into an O-terminated one after the removal of the Ga on the surface. The optoelectronic performance, including the responsivity and response/decay characteristics, was greatly improved, indicating the effective removal of defects by PEC etching. Our findings are expected to play an important role in the fabrication of an ultra-wide bandgap β-Ga₂O₃ semiconductor devices, thus paving the way for improved optoelectronic device performance.