Metalorganic chemical vapor deposition growth of Cd1−yZnyTe epitaxial layers on GaAs and GaAs/Si substrates

Abstract

As a step toward growth of HgCdTe on GaAs and GaAs/Si substrates, Cd1–yZnyTe buffer layers were grown on these substrates. A conventional pyrolytic process at relatively high temperature (441 °C) was used. Epitaxial growth on GaAs was achieved for all alloy compositions, 0≤y≤1. The solid–vapor distribution curve for alloy deposition was determined experimentally for one particular set of deposition parameters, and compared with a thermodynamic model. Deposit uniformity was also studied experimentally and compared with a model incorporating coupled fluid dynamics and mass transport (but not chemical kinetics) with realistic reactor boundary conditions and thermal effects. Epitaxial growth on the GaAs(123) substrates orientation was studied by x-ray techniques. Cd1–yZnyTe epitaxial layers grown on these substrates were tilted with respect to the substrate toward 〈111〉, about a 〈12̄1〉 axis. The degree of tilt depended on the alloy composition y, ranging from 1.7° for y=1 to 3.2° for y=0. These results are consistent with a model of the GaAs(123) surface as a terraced structure consisting of (111) oriented ledges and steps parallel to [12̄1]. The crystal lattice perfection of the epitaxial layers was assessed by x-ray double-crystal rocking curve analysis. The best full width at half-maximum (FWHM) obtained for CdTe layers was 80 arc s, and for ZnTe layers it was 150 arc s. Cd0.96Zn0.04Te layers also grown on GaAs/Si(001) tilted 3.5° toward 〈111〉. Some layers grown on these substrates also had rocking curve FWHM≤100 arc s. Hg0.7Cd0.3Te was grown by liquid phase epitaxy on a CdZnTe/GaAs/Si substrate, and the resulting layer had a rocking curve FWHM of 165 arc s.