Photoelectrochemical Etching of Sn‐Doped (−201) and (001) β‐Ga ₂ O ₃ in a NaOH Solution

Photoelectrochemical (PEC) etching is an alternative technique that can overcome the limitations of conventional wet etching, which has difficulty in achieving practical etch rates for β‐Ga 2 O 3 because of its high chemical stability and bond strength. In this work, we demonstrate PEC etching of Sn‐doped (−201) and (001) β‐Ga 2 O 3 in a 6 M NaOH solution and the etch rate dependence on the etchant solution temperature and applied bias. PEC etch rate of both (−201) and (001) β‐Ga 2 O 3 is found to be a strong function of the applied bias and to increase with increasing solution temperature. The activation energies for PEC etching of (−201) and (001) β‐Ga 2 O 3 with +15 V bias are 0.54 and 0.31 eV, respectively, suggesting that the etching is reaction‐limited. However, increasing the bias to +25 V results in a shift to diffusion‐limited etching with activation energies of 0.125 and 0.119 eV, repectively. The etch reaction is observed to proceed selectively and relatively uniformly in the UV light‐irradiated regions, and the PEC‐etched surface exhibits a Ga‐deficient composition. Maximum etch rates of ~4.81 and ~4.86 μm/min are obtained for (−201) and (001) β‐Ga 2 O 3 , respectively, under a condition of +25V, 90°C, 6 M NaOH, and 500 W lamp power.