Morphological, Structural and Optical Characteristics of Porous GaN Fabricated by UV-Assisted Electrochemical Etching

Abstract

The fabrication of porous GaN (PGaN) by UV-assisted electrochemical etching with a variations of current densities (40, 60, and 80 mA/cm2) for 60 min in electrolytes consisting of 4% KOH are reported. Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-Ray (EDX), Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) were used to characterize the morphological and structural characteristics of the PGaN. All PGaN sample prepared by electrochemical etching technique produced a hexagonal-like pore shape. FESEM images demonstrated that the pore uniformity and porosity are affected significantly by the current density. The PGaN sample fabricated with 80 mA/cm2 produces a uniform and high porosity structure compared to other PGaN sample. This shows that the morphology and structural characteristic of PGaN are increase with the increase of current density. The EDX result revealed significant Ga and N atom presence in all samples. However, the O atom only presence in sample etched with 80 mA/cm2 implying that the etching process is occur vigorously in this sample. The AFM verified that the surface roughness and the pore depth are increased as current density increased. There were relatively large variations of the peak intensities for 2Theta-scan patterns as exposed by XRD. The peak shift for PGaN sample relative to as-grown was inconsistent and the changed was relatively small. Raman intensity found to be enhanced with the increase in current density and among the PGaN sample, the E2(high) peak for sample prepared with 60mA/cm2 and 80mA/cm2 was observed to be slightly shifted to lower frequency. The PL spectra displayed that the porosity has high impact on the PL peak intensity. . Overall, this proved that with the usage of low power UV light, the pore structure still can be produced as good as pore structure fabricated with high power UV light.