Cathodoluminescence microscopy and spectroscopy of GaN epilayers microstructured using surface charge lithography

Abstract

Cathodoluminescence (CL) microscopy and spectroscopy have been used to investigate the optical properties of GaN microstructures patterned by Ar+ ion irradiation and subsequent photoelectrochemical (PEC) etching. Monochromatic CL images and CL spectra reveal an enhancement of several defect-related emission bands in a 10 mu m wide area around each microstructure. In addition, columnar nanostructures and nanoetch pits were found in the PEC etched areas. CL emission of the nanocolumns is dominated by free electron to acceptor transitions, while excitonic luminescence prevails in the rest of the etched GaN layers. Investigation of the sidewalls of the microstructures reveals that a CL emission band centered at about 3.41 eV, attributed to excitons bound to structural defects, is effectively suppressed after PEC etching only in the observed nanocolumns.