Growth of In 0 . 5 2 Al 0 . 4 8 As epilayers on InP(100) substrates by molecular beam epitaxy at a wide range of substrate temperatures (470-550 °C) and at high arsenic beam equivalent pressures is carried out. Analysis performed using low-temperature photoluminescence (PL) and double axis X-ray diffraction (XRD) showed a strong dependence of the PL and XRD linewidths and lattice-mismatch on the substrate temperature, with minimum linewidths and lattice-mismatch occurring between approximately 500 and 520 °C. The XRD intensity ratio (Int e p i /Int s u b ) varied in opposition to the lattice-mismatch, with higher intensity ratios corresponding to lower lattice-mismatches. From the X-ray diffraction curves of samples grown at low temperatures, it was observed that the main peak associated with the InAlAs epilayer is comprised of smaller peaks, which strongly indicates disordering owing to the presence of alloy clustering. PL spectrum taken at increasing temperatures showed the quenching of the main emission peak followed by the evolution of a distinct peak at lower energy, possibly associated with carrier localization due to the presence of lattice disorder. In addition to the InAs-like and AlAs-like longitudinal-optic (LO) phonon modes at 234 cm - 1 and 370 cm - 1 , respectively, Raman scattering measurements also showed an additional higher energy mode at 273 cm - 1 in the samples grown at lower temperatures approaching 470 °C. Within the range of V/III flux ratios investigated (32-266), the lowest PL linewidth of 14 meV was recorded for the samples grown at a V/III ratio of 160 at a substrate temperature of 510 °C. The lattice-mismatch between the epilayer and the substrate for these samples was also found to be relatively insensitive to changes in the V/III flux ratios.
