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.