Effect of ultraviolet and room lights on porous GaN films using photo-assisted electrochemical etching

We fabricated high reflectivity GaN/nanoporous (NP) GaN distributable Bragg reflector (DBR) structures by electrochemical etching of HF solution in ultraviolet (UV)- and room-light. Compared with in room-light, the DBR fabricated in UV-light has higher reflectivity. To elucidate the difference of these two DBRs, the effect of lights on the etching breakdown voltage, pore morphology, crystal quality and photoluminescence (PL) properties was studied in detail. By comparison, the NP-GaN film obtained under the UV-light has lower breakdown voltage, higher porosity, higher crystal quality and bigger red-shift of PL position, meaning that the DBR obtained in the UV-light has higher quality and reflectivity.