Zn0.85Cd0.15Se active layers on graded-composition InxGa1−xAs buffer layers

We investigated the structural and optical properties of Zn0.85Cd0.15Se epilayers for blue optical emission on lattice-matched InxGa1−xAs buffer layers. Both the II–VI layers and the III–V buffers were grown by molecular beam epitaxy on GaAs(001) wafers. A parabolic In concentration profile within the graded-composition InxGa1−xAs buffers was selected to control strain relaxation and minimize the concentration of threading dislocations. Dislocation-free II–VI growth was readily achieved on the graded buffers, with a Rutherford backscattering yield ratio reduced by a factor of 3 and a deep-level emission intensity reduced by over two orders of magnitude relative to those observed following direct II–VI growth on GaAs. The surface morphology of the materials, however, was found to replicate the crosshatched pattern of the underlying InxGa1−xAs substrates.