Large-sized 2D semiconductor materials have gained significant attention for their fascinat-ing properties in various applications. In this work, we demonstrate the fabrication of nanoperforated ultrathin β-Ga₂ O₃ membranes of a nanoscale thickness. The technological route includes the fabrication of GaN membranes using the Surface Charge Lithography (SCL) approach and subsequent thermal treatment in air at 900^◦ C in order to obtain β-Ga₂ O₃ membranes. The as-grown GaN membranes were discovered to be completely transformed into β-Ga₂ O₃, with the morphology evolving from a smooth topography to a nanoperforated surface consisting of nanograin structures. The oxidation mechanism of the membrane was investigated under different annealing conditions followed by XPS, AFM, Raman and TEM analyses.