Structural and optical properties of InP1-xSbx/n-InAs epilayers grown by gas source molecular beam epitaxy

High-resolution x-ray diffraction (HR-XRD), photoluminescence (PL), synchrotron radiation extended x-ray absorption fine-structure (SR-EXAFS) measurements are methodically analyzed for assessing the optical and structural properties of InP1-xSbx/n-InAs epifilms grown by gas-source molecular-beam epitaxy method. For InP0.63Sb0.37/n-InAs sample, the PL study has revealed two A(1), A(2) energy bands. The A(1) band prevalent at low temperature is attributed to the recombination of carriers trapped in the tail states. The A(2) band with nearly constant transition energy similar to 0.46 eV is virtually temperature independent. In InP1-xSbx alloys, the energy peak of A(1) band redshifted with temperature and showed strong compositional disorder. The A(2) band, dominant at higher temperature with Gaussian-like line shape is ascribed to the deep-level transition as its behavior coincided with the signature of a configuration coordinate model. The deep level responsible for A(2) band is possibly linked to the "vacancy-impurity" like complexes having ground and excited states in the energy band gap. The composition dependent analysis of SR-EXAFS data for InP1-xSbx/InAs samples has confirmed the maintenance of nearest neighbor In-P, In-Sb shell distances within the range of bulk binary materials' bond lengths. We feel that our results of HR-XRD, PL and SR-EXAFS techniques have provided valuable information on the structural and optical characteristics of the InP1-xSbx/n-InAs (001) epilayers and can be extended to many other technologically important materials.