The growth of various buffer layer structures and their influence on the quality of (CdHg)Te epilayers

Abstract

The suitability of various buffer layer structures on (100) GaAs for (CdHg)Te growth by organometallic vapour phase epitaxy (OMVPE) was investigated. The preferred epitaxial orientation of (100) GaAs/ (lll) CdTe was found to be unsuitable due to the formation of electrically active defects in the material. An intermediate ZnTe layer was used to select the (100) orientation and (100) CdTe layers were then deposited on this ZnTe layer. The quality of the resultant CdTe buffer was found to critically depend on the thickness of this intermediate ZnTe buffer, with a ZnTe thickness of approximately 500 angstrom producing the best CdTe buffer. (CdHg)Te epilayers grown on these ZnTe/CdTe buffers had improved electrical properties, but still suffered from a poor surface morphology. This surface morphology could be improved by using a lattice matched Cd0.96Zn0.04Te alloy as the final buffer layer, but the surface pyramids typical of the (100) orientation could never be completely eliminated.