Spectroscopic investigation of porous GaAs prepared by laser-induced etching

We have investigated the etching mechanism in Cr–O doped GaAs wafer under super- and sub-bandgap photon illumination. A comparison of the etching rate and properties of nanostructures from two samples which are etched with argon-ion laser (2.41 eV) and Nd:YAG laser (1.16 eV), are presented here. The etching mechanism is found different for these different illuminations, which play the key role in the formation of defects. It is observed that the etching process starts vigorously under sub-bandgap photon illumination through the mediation of intermediate defect states. SEM micrograph shows the formation of distinct GaAs nanostructures in sample etched by Nd:YAG laser. Porous structure produced by Nd:YAG laser shows strong room temperature luminescence in the red region. The size and size distribution of the nanocrystals are investigated by non-destructive Raman and photoluminescence spectroscopies. The data are analyzed within the framework of quantum confinement models.