Morphological evolution and characterization of GaN pyramid arrays fabricated by photo-assisted chemical etching.

GaN pyramid arrays have been successfully synthesized by selective photo-assisted chemical etching in a K 2 S 2 O 8 /KOH solution. A detailed analysis of time evolution of surface morphology has been conducted, which describes an etching process of GaN pyramids. Room temperature cathodoluminescence images indicate that these pyramids are composed of crystalline GaN surrounding dislocations, which is caused by the greater recombination rate of electrons and holes at dislocation than that of crystalline GaN. The Raman results show a stress relaxation in GaN pyramids compared with unetched GaN. The optical property of both unetched GaN and GaN pyramids has been studied by photoluminescence. The formation mechanism and feature of GaN pyramids are also rationally explained. [ABSTRACT FROM AUTHOR]