A half-metallic isolated band in the band-gap of GaAs and GaP semiconductors has been found for Ti and Sc transition metal impurities and proposed as highly-efficient photovoltaic materials. In this paper, we have investigated by first principle calculations, the spin polarized and non-polarized dispersion band structures and lattice constants of Ga3As4Ti and Ga4As3Ti alloy semiconductor compounds. We have carried out a comparative study of these compounds in order to identify the basic features of the isolated intermediate band formation in the semiconductor band-gap. We use an ab-initio fully self-consistent density functional theory method in the local density approximation (LDA), with norm-conserving, non-local pseudopotentials for core electrons. To assess the results, we first determined the electronic properties of GaAs and compared them with the experimental results. We find that spin wave functions of the polarized GanAsmTi compounds noticeably modify the nature and properties of the intermediate band that have already shown in the corresponding paramagnetic compounds. (C) 2005 Springer Science + Business Media, Inc.