Surface morphology and formation of GaAs nanocrystals by laser-induced etching: SEM, PL and Raman studies

GaAs nanostructures were prepared by a laser-induced etching process using a Nd:YAG (λ=1.06 μm) laser. Scanning electron microscope (SEM) was used to monitor changes in surface morphology produced on etching. The etched samples were subjected to photoluminescence (PL) and Raman spectroscopic investigations using an argon-ion laser of excitation energies of 2.54 and 2.71 eV. PL spectra from etched GaAs shows two broad luminescence bands along with a red shift in comparison to a sharp band in the unetched GaAs. Raman measurements exhibit enhancement of first-order LO mode peak intensity in the etched sample along with line-shape asymmetry and shifting of mode towards lower frequency with increasing laser excitation energy. Both Raman and photoluminescence results were explained using quantum confinement models involving Gaussian size distribution of nanocrystallites constituting of GaAs nanostructures. There is reasonable agreement between the results obtained from photoluminescence and Raman spectroscopic investigations of the etched GaAs samples.