Spatially resolved cathodoluminescence of GaN nanostructures fabricated by photoelectrochemical etching

Abstract

The emission properties of GaN nanostructures created by photoelectrochemical etching have been investigated by cathodoluminescence (CL) in the scanning electron microscope. Columnar structures with diameters of 150–250 nm formed near the surface of the as-grown GaN layers branch into nanowires with diameters of 20–60 nm, while islands with coral-like relief were observed at the bottom of the etched areas. CL emission of the observed nanostructures is dominated by free electron to acceptor transitions. Local CL spectra provide direct evidence of the existence of either compressive or tensile stress in different nanostructures. No free exciton luminescence was observed in GaN nanowires, supporting their relation to threading dislocations.