​Gallium nitride GaN, a wide-bandgap III-V semiconductor material with a bandgap wavelength λg = 366 nm forWurtziteGaN and transparency window covering the visible spectrum, has a large number of applications for photonics and optoelectronics. However, the optical quality of this material suffers from growth imperfections due to the lack of a suitable substrate. Recent studies have shown that GaN grown on −201 β − Ga2O3 galliumoxide has better lattice matching and hence superior optical quality as compared to GaN grown traditionally on Al2O3 sapphire. In this work, we report on the fabrication of GaN waveguides on Ga2O3 substrate, followed by a wet-etch process aimed at the reduction of waveguide surface roughness and improvement of side-wall verticality in these waveguides. The propagation loss in the resulting waveguides has been experimentally determined to be 7.5 dB/cm.​