Morphology, Raman scattering and photoluminescence of porous GaAs layers

Raman scattering (RS), photoluminescence (PL), optical reflectance spectra, AFM, SEM, XPS have been measured to study porous films of GaAs, obtained by electrochemical etching in HF:H2O or HF:C2H5OH:H2O electrolyte. The two-layer structure was found to have the size of pores in the range of 0.2–1.0 μm, and to contain Ga2O3, As2O3 as well as other oxides and GaAs nanocrystals. The intensity of RS for porous surfaces is higher than for the flat ones. The position of LO-, TO-phonon lines and their half-width depend on the wavelength of exciting light and the electrochemical etching technology. Evidences for quantum confinement of phonons and excitons were obtained in RS and low temperature PL spectra, respectively. From the quantum confinement of excitons, the radius of GaAs nanocrystals is estimated as 5–8 nm.