Enhanced optical properties of porous GaN by using UV-assisted electrochemical etching

In this paper we report the fabrication of porous GaN by UV-assisted electrochemical etching with direct current densities of 5, 10 and 20 mA/cm2 for 20 min in electrolytes consisting of aqueous HF and ethanol C2H5OH (1:4). Scanning electron microscopy (SEM) demonstrates that current density has significant effect on the size and shape of the pores. Raman spectra of both as-grown and porous GaN exhibit phonon mode E2 (high), A1 (LO), A1 (TO) and E2 (low). There was a red shift in E2 (low) and E2 (high) and blue shift in A1 (LO). The red shift in E2 (high) indicates a relaxation of compressive stress in the porous GaN surface with respect to the underlying single crystalline epitaxial GaN. Peak intensity of photoluminescence (PL) spectra of the nanoporous GaN samples was observed to be enhanced and the crystal quality was improved with increase in etching current density as compared to as-grown GaN.