Porous Ga ₂ O ₃ and defect selective etching via electrochemical path

Abstract β ‐Ga₂O₃ is a promising ultra-wide-bandgap semiconductor for power and deep-ultraviolet devices, yet its strong Ga–O bonds make controllable etching and defect delineation challenging. In this work, we systematically investigate the electrochemical etching of cast-grown (100) β -Ga 2 O 3 substrates in 85 wt% phosphoric acid over an etching time range of 20–60 min and reveal a tunable transition from porous surface treatment to defect-selective etching. At low anodic bias the etching proceeds in a time-dependent reaction-limited regime, where randomly distributed pores are formed on the surface. Additionally, above a critical bias (∼15 V), etching becomes defect-selective at room temperature, forming olive-shaped surface pits aligned along the [010] direction, correlating strongly with dislocations, voids, and stress-concentrated regions. It is demonstrated that the etching process is governed by the coupled kinetics of interfacial anodic dissolution and phosphate deposition–removal. This simple electrochemical strategy enables both porous structuring and defect revelation, offering a new route for substrate assessment and device engineering.