Structural and optical investigations of high quality InGaAs/InAlAs short period superlattices grown on an InGaAs quasisubstrate Available to Purchase

Unstrained InGaAs (4.5 nm)/InAlAs (1.0 nm) short‐period superlattices grown on a (100) GaAs substrate were studied. To achieve this growth, an In‐composition‐graded buffer layer and a thick InGaAs buffer layer were adopted. Structural properties were investigated by x‐ray diffraction, atomic force microscopy, and a compositional analysis by the thickness fringe method. X‐ray diffraction patterns showed clear periodicity in the superlattices and atomic force spectroscopy images showed cross‐hatch morphology for the main ridge along the (011̄) direction. Clear thickness fringes in the bright‐field electron microscope images for the superlattice region and ambiguous fringes for the graded buffer layer indicate that misfit dislocation due to lattice mismatch concentrates in the graded buffer and a high‐quality superlattice is successfully grown in spite of the large lattice mismatch between the superlattice and the substrate. Optical characteristics measured by photocurrent spectroscopy reveal a clear Wannier–Stark localization effect at room temperature. The experimental absorption energies agree well with calculated values by a transfer matrix method using parameters for bulk InGaAs and InAlAs.