Silicon doping in In0.52Al0.48As layers grown by molecular beam epitaxy: characterization of material properties

In0.52Al0.48As layers at different silicon doping levels are analysed by low temperature photoluminescence (PL), Raman spectroscopy and Hall effect measurements. The PL peak energy exhibits a horizontal S-shaped dependence at increasing temperature, an effect which is more prominent at lower doping levels but weakened owing to a possible reduction in the donor activation energy at higher doping levels. The frequencies of both the AlAs-like and the InAs-like longitudinal optic (LO) phonon modes decrease and the LO phonon line shape broadens as the doping level is increased. The PL intensity also showed in increasing degree, at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials. The temperature dependence of the Hall mobility exhibits clear contributions μi and μpo from ionized impurity and polar optical phonon scattering at low and high temperatures respectively in the samples with low and moderate doping levels. Our data suggest a solubility limit of about 8 x 1018 cm−3 for silicon doping in the InAlAs material.