GaAs nanoparticles have been deposited on the indium tin oxide-coated glass substrate by the electrodeposition technique at 75 K. Transmission electron microscope micrographs show the isolated particles with diameters ranging from 11 to 21 nm and the connected particles having larger sizes. Selected area diffraction patterns contain spotty rings showing the polycrystalline nature of the GaAs nanocrystals. The interplanar spacings, determined from the electron diffraction pattern and the high-resolution lattice image, correspond to that of the orthorhombic GaAs(III) phase normally observed under high pressure. Two broad peaks corresponding to the above phase have been detected in the X-ray diffraction spectra. Micro-Raman measurement at 300 K shows a defect-activated phonon mode occurring at about 250 cm(-1) assigned to a point defect created due to the arsenic vacancy. The above vacancy arises during the transition from the six-fold co-ordination to the four-fold co-ordination phase. (C) 2004 Elsevier B.V. All rights reserved.