We demonstrate a catalyst-free method to grow lateral InAs nanowires on GaAs (1 0 0) substrate by means of molecular beam epitaxy. By applying pre-surface treatment under oxygen plasma, lateral InAs nanowires with lengths of 1-2 mu m and width of approximately 30-80 nm are epitaxial grown along [1 <(1)overbar> 0 ] direction. Stacking faults are not observed in the epitaxial process, which is usually an issue for InAs nanowires grown vertically on (1 1 1) substrates. Photo-luminescent measurements were performed for both single and multiple layers of InAs nanowires. A spectrum peak at the wavelength of 1625 nm is observed for a single wire at 5 K and room temperature emission is obtained for three layers of InAs nanowires. In addition, InAsSb nanowires are achieved along [1 1 0] direction, with a length of 0.4-0.8 mu m and a width of 60-80 nm.