The characteristics of Si-doped In0.52Al0.48As layers as a function of the silicon doping are analyzed by low-temperature photoluminescence (PL), Raman spectroscopy and Hall effect measurements. Analysis of the PL intensity at increasing silicon doping levels showed a temperature dependence which is characteristic of disordered and amorphous materials, suggesting a behaviour which has the characteristic of disordered materials at higher doping levels. The PL linewidth broadens at higher silicon doping levels while the Raman scattering spectra showed a reduction in both the AlAs-like and InAs-like longitudinal-optic (LO) phonon frequencies coupled with a broadening of the LO phonon line shape as the doping level is increased.