INFLUENCE OF A ZNTE BUFFER LAYER ON THE STRUCTURAL QUALITY OF CDTE EPILAYERS GROWN ON (100)GAAS BY METALORGANIC VAPOR-PHASE EPITAXY

The influence of a ZnTe buffer layer on the structural quality of CdTe epilayers grown on (100)GaAs substrates by metalorganic vapor phase e pitaxy has been investigated by both x-ray diffraction and ion channel ing Rutherford backscattering spectrometry measurements. Single-crysta l (100) oriented CdTe epilayers of good structural quality have been o btained after inserting a ZnTe buffer layer of a thickness ranging bet ween 300 and 500 nm. The influence of the buffer layer thickness on th e crystalline quality and the morphology of the CdTe epilayer has been related to the defect distribution and the surface roughness of the Z nTe buffer layer. The crystalline quality and the surface strain have been thus studied as a function of the CdTe thickness on samples havin g optimal ZnTe layer thickness. The initial compressive mismatch betwe en CdTe and ZnTe, f = -5.8%, appears to be almost fully relaxed for a CdTe thickness around 200 nm. A residual compressive in-plane strain ( about -0.02%), independent of the CdTe epilayer thickness, has been fo und above 300 nm which can be ascribed to thermal strain and indicates a complete relaxation of the lattice misfit at the growth temperature . (C) 1996 American Vacuum Society.