Properties of porous gallium nitride under varying etching durations of low temperature photoelectrochemical etching

Abstract

In this work, the porous gallium nitride (PGaN) samples were fabricated via photoelectrochemical etching (PEC) at low temperature (LT) condition. The effect of etching duration during the low temperature photoelectrochemical etching (LT-PEC) on the structural and morphological properties of PGaN structures was investigated. A continuous current density of 60 mA/cm² and potassium hydroxide (KOH) electrolyte was used during the etching process at different etching durations of 40, 60, and 90 minutes. The field emission scanning electron microscopy (FESEM) images revealed that PGaN etched for 60 minutes had the smallest pore diameter (27.23 nm) and highest estimated porosity (36.0 %). Its pore diameter and the estimated average pore depth also increased as the duration increased. Furthermore, the atomic force microscopy (AFM) measurement revealed that the root mean square (RMS) surface roughness increased as the etching duration increased. The Raman spectra of E₂(high) phonon mode of all the PGaNs had shifted to lower frequency than that of the as-grown GaN due to the stress relaxation. Lastly, the intensities of the Raman spectra of the PGaNs increased as the duration increased, indicating more efficient light scattering in their porous structures. Therefore, the enhanced PGaN properties indicate that they possess good potential for implementation in sensing devices application.