Patterned heteroepitaxial processing applied to ZnSe and ZnS0.02Se0.98 on GaAs (001)

Abstract

We have demonstrated the patterned heteroepitaxial processing (PHP) approach for the removal of threading dislocations (TDs) from ZnSe and ZnS0.02Se0.98 on GaAs (001). PHP involves the growth of a continuous heteroepitaxial layer followed by postgrowth patterning and annealing. We found that the basic mechanism of TD removal by PHP is thermally activated dislocation motion in the presence of sidewalls. By studying the temperature dependence we showed that the activation energy for the annealing process (∼0.7 eV in ZnSe on GaAs) is consistent with dislocation motion by glide. We showed that there is a minimum mesa thickness required for the complete removal of TDs by PHP (∼3000 Å for 70 μm×70 μm mesas of ZnSe on GaAs). This is because the lateral forces acting on TDs are proportional to the mesa thickness. We also conducted a preliminary study of the mismatch dependence of PHP. Our results suggest that PHP removes TDs more effectively in the higher lattice mismatch system ZnSe/GaAs (001) than in the lower lattice mismatch system ZnS0.02Se0.98/GaAs (001). This is expected based on the mismatch dependence of the line tension forces in the misfit segments of dislocations.