Novel optical and structural properties of porous GaAs formed by anodic etching of n+-GaAs in a HF:C2H5OH:HCl:H2O2:H2O electrolyte: effect of etching time

Abstract

Porous GaAs layers have been formed by anodic etching of n +-type GaAs (10.0) substrates in a HF:C2H5OH:HCl:H2O2:H2O electrolyte. A dramatic impact of etching time on the optical and structural properties of porous GaAs layer is demonstrated. The nano/micro-features of porous GaAs layers are revealed by scanning electron microscopy (SEM) imaging. Two-peak room temperature photoluminescence (PL), “blue-green” and “green-yellow”, is obtained in all prepared porous GaAs samples. Proper adjustment of etching time is found to produce a white color layer, instead of the usual dark gray color of porous GaAs. This is found to cause vast enhancement in the intensity of the visible PL in porous GaAs layer. Chemical composition and structural characterization by means of X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and micro-Raman spectroscopy, confirm that this layer is characterized with monoclinic β-Ga2O3 rich surface. Etching time induced—modification of structural and chemical properties of porous GaAs layer is discussed and correlated to its PL behavior. It is inferred that the “blue-green” PL in porous GaAs can be ascribed to different degrees of quantum confinement in GaAs nanocrystallites, whereas, the “green-yellow” PL is highly influenced by the As2O3 and Ga2O3, content in the porous GaAs layer. In addition, the reflectance measurements reveal an anti-refection trend of behavior of porous GaAs layers in the spectral range (500–1,100 nm).