Structural and optical properties of electrochemically etched p + -type GaAs surfaces: influence of HF presence in the etching electrolyte

Porous GaAs layers have been prepared by electrochemical etching of p +-type GaAs (10 0) surfaces in two different solutions; HCl: H2O2: H2O (HF free electrolyte) and HCl: H2O2: H2O: HF: C2H5OH (HF electrolyte). Under the same equivalent etching condition, naked eyes observations reveal the formation of a white color layer on the top of the sample formed in the HF electrolyte, while the sample in the HF free electrolyte exhibited the ordinary gray color layer of porous GaAs. Scanning electron microscope (SEM) observation revealed the impact of presence of HF in the electrolyte on surface topography of the layer. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and micro-Raman scattering investigations demonstrate that the use of HF electrolyte leads to formation of GaF3 *3H2O and enhances the formation of As2O3 (arsenolite) in the layer. This is found to result in a remarkable improvement in the intensity of the room temperature photoluminescence (PL). The intensity of “green” PL band of the layer formed in the HF electrolyte is found to be about 40 times higher than that formed in the HF free electrolyte.