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-shape d dependence at increasing temperature, an effect which is more promin ent at lower doping levels but weakened owing to a possible reduction in the donor activation energy at higher doping levels. The frequencie s of both the AlAs-like and the InAs-like longitudinal optic (LO) phon on 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 characteri stic of disordered and amorphous materials. The temperature dependence of the Hall mobility exhibits clear contributions mu(i) and mu(po) fr om ionized impurity and polar optical phonon scattering at low and hig h temperatures respectively in the samples with low and moderate dopin g levels. Our data suggest a solubility limit of about 8 x 10(18) cm(- 3) for silicon doping in the InAlAs material.