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Photoelectrochemical etching (PEC) of n+-GaN in KOH and AZ400K photoresist developer is presented. We compare the two solutions used for PEC etching without an external bias. The influence of etchant concentration and of the intensity of ultraviolet illumination was studied with emphasis on the resulting etched surface quality. The quality of the shallow etched surface and its roughness are presented. The AZ400K etchant was applied to shallow etching of n+-GaN with threading dislocation densities in the range of 109–1010 cm−2. Moreover, the first analysis of photocurrent monitoring during the electrochemical etching of GaN epitaxial layers in KOH is presented. We found that photocurrent very sensitively reflected the changes in the quality of the etched surface.

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Copper oxide thin films were obtained using pulsating spray pyrolysis method. The morphological, structural, and optical properties of fabricated films were studied. X-ray analysis revealed that the CuO thin films are single-phase. The study of films morphology by SEM and AFM methods showed that the obtained films have a fairly high surface roughness and contain grains of different shapes and sizes. It was found that the obtained films of copper oxide have high values of the absorption coefficient, which confirms the possibility of their use as absorbing layers for solar cells. The obtained values of the optical band gap of the material are in the range from 1.45 eV to 1.60 eV. Raman spectroscopy revealed three modes A1g, B1g, and B2g, of the crystal structure of monoclinic CuO. The devices based on p-type copper oxide are promising for solar cells fabrication because they can reduce production costs, due to their low cost and inexpensive production methods compared to silicon solar cells fabrication.

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