The effects of Si doping in In0.52Al0.48As layers grown lattice matched on InP substrates

The characteristics of Si-doped In0.52Al0.48As layers as a function of silicon doping ranging from 1×1017 to 4×1018 cm−3 are analyzed by low-temperature photoluminescence (PL), Raman spectroscopy, and Hall effect measurements. When the sample temperature is increased from 4 K, the PL peak energy exhibits an inverted S-shaped dependence which is characteristic of carrier localization. This effect was more prominent at lower doping levels, but weakened at high doping levels due to a possible reduction in the donor binding energy. The peak energy variation at temperatures higher than ≊100 K follows the usual band-edge variation with temperature, suggesting that the PL arises from band-to-band transitions. While the PL linewidth of the undoped and moderately doped samples decreases and then increases with temperature, a near-monotonic increase in the linewidth due to thermal broadening was observed in highly doped samples. Supported by observations of a reduction in both the AlAs-like and InAs-like longitudinal-optic (LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.