A new diluted magnetic III-V semiconductor In1-xMnxAs1-ySby was grown by metalorganic molecular beam epitaxy. Raman scattering measurements were performed on InMnAs samples. The recorded spectra showed coupled LO phonon-plasmon mode. The behavior of this coupled LO phonon-plasmon mode indicated that InMnAs layers are p-type. The light-induced ferromagnetic order was confirmed in the InMnAs layers and was observed, fur the first time, in the InMnAsSb/InSb heterostructures under the irradiation of long wavelength (> 2 mum) light. The results are explained in terms of hole accumulation in the InMnAsSb layer, which enhances the ferromagnetic spill exchange among Mn ions. The sample with InMnAsSb layer grown on InSb at 250 degreesC showed larger ferromagnetic order than that Brown at 280 degreesC.