GaInAs/InP multilayer structures have been grown by chemical beam epitaxy in windows opened in Si0 2 masks deposited on (001) InP substrates. The windows were narrow lines of width varying between 20 and 2μm, oriented along the [011_] direction. The growth conditions, substrate temperature and V/III ratio were adjusted to minimize the growth on the masked areas and to create (111) facets along the mesa. The samples were studied using a field emission scanning electron microscope and by low temperature photoluminescence. The diffusion of In and Ga species from the (111) planes towards (100) observed for the growth of InP and GaInAs enhances the growth rate on the (100) plane and changes the composition of the ternary layer. This gives rise to a red shift of the photoluminescence spectra from the GaInAs layers that depends on the initial width of the line. This diffusion can be used to design crescent quantum wires or nanodevices whose band gap varies with the width of the line.