(GaAs)1−x(Si2)x metastable alloys grown on (001), (110), (112), and (111) GaAs substrates, with Si fractions in the range 0⩽x⩽0.43, were studied by Raman scattering. Two modes near the LO and TO modes of GaAs, besides two local modes associated either with Si–As or Si–Ga and Si–Si bonds, are observed in the Raman spectra. The ratio of integrated intensities of TO-like and LO-like modes (ITO/ILO) is used to evaluate the short range order. It is observed that the zinc blende to diamond transition reported in the literature for these alloys does not influence the Si fraction dependence of the short range order. © 2001 American Institute of Physics.