We report on fabrication of ultra-thin GaN membranes of nanometer scale thickness, by using the concept of surface charge lithography based on low-energy ion treatment of the sample surface with subsequent photoelectrochemical etching. Both nanoperforated and continuous membranes have been fabricated depending on the energy and dose of the ions. These membranes are transparent to UV radiation, emit mainly yellow cathodoluminescence and exhibit electrical conductivity. Successful fabrication of nanometer-thin membranes opens unique possibilities for exploration of two dimensional GaN-based structures predicted to be ferromagnetic with half-metallic or metallic configuration which is of peculiar importance for spintronics applications.