[en] MOCVD and LPE technologies of deposition of GaAs and AlGaAs layers onto (100) GaAs substrates with a developed surface area are developed. Porous GaAs layers and surface microprofiles of dendrite and quasi-grating types were fabricated on these substrates. The quality of layers was determined in comparative studies of the surface morphology and X-ray diffraction. Further, photovoltaic converters based on these layers have been devised. The best parameters among the samples under study were attained in photovoltaic converters based on the layers with the dendrite-type microprofile of substrate, which had the most developed area of the working surface and the dislocation density of 10⁴ cm^-2. In particular, at the wavelength of 0.65 μm, the external quantum efficiency of these photovoltaic converters was 150% higher than in the reference samples produced on a smooth surface