Size-selective laser-induced etching of semi-insulating GaAs: Photoluminescence studies

The size-selective laser-induced etching of semi-insulating GaAs 〈1 0 0〉 is carried out to create a porous structure by varying the laser beam exposure time. The etch-time dependent photoluminescence (PL) spectroscopy results show that a direct tuning of the size of the nanocrystallites has a limit and it can be effectively carried out till the oxides layers developed on the top surface make a damping in the redox reaction process. The etch rate ∼0.3–0.5 nm/s is observed in the initial state and it continued with much slower rate for longer etching duration. The formation of GaAs nanostructures as well as chemical reaction byproducts on the top surface is observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). An estimate of the etch-time dependent nanocrystallite size and its size distribution on the etched layer is obtained by using the quantum confinement model.