We report on the capabilities of electrochemical and photoelectrochemical etching technologies for the fabrication of multilayer porous structures based on GaN substrates grown by Hydride Vapor Phase Epitaxy (HVPE) and Metal Organic Chemical Vapor Deposition (MOCVD) methods. The formation of multilayer porous structures during etching of GaN is caused by the spatial modulation of the electrical conductivity throughout the surface and the volume of the HVPE-grown substrates, which occurs according to a previously proposed model involving generation of pits and their overgrowth. Since these domains consist of sheets with alternating conductivity, they are intrinsically suitable for producing multilayer porous structures, without any additional technological procedures for growing layers with controlled conductivity, as in the case of MOCVD growth of GaN. The results of this study demonstrate that the porosity of layers within the multilayer porous structure is controlled by several technological parameters, such as the composition of electrolytes, their concentration, and the anodization potential applied during electrochemical etching. Multilayer porous structures with a controlled design have been produced by optimizing the technological process of electrochemical etching of MOCVD-grown samples, consisting of five pairs of thin layers with alternating doping profiles. The samples have been characterized by SEM imaging, photoluminescence spectroscopy, and micro-reflectivity measurements. In the presentation, the applicability of the produced porous structures for the design and fabrication of Bragg reflectors will be demonstrated.