Metalorganic chemical vapor deposition growth of Cd_1−yZn_yTe epitaxial layers on GaAs and GaAs/Si substrates

As a step toward growth of HgCdTe on GaAs and GaAs/Si substrates, Cd_1–yZn_yTe 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. Cd_1–yZn_yTe 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. Cd_0.96Zn_0.04Te 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. Hg_0.7Cd_0.3Te 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.