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

Abstract

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 A1, A2 energy bands. The A1 band prevalent at low temperature is attributed to the recombination of carriers trapped in the tail states. The A2 band with nearly constant transition energy ∼ 0.46 eV is virtually temperature independent. In InP1−xSbx alloys, the energy peak of A1 band redshifted with temperature and showed strong compositional disorder. The A2 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 A2 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.