EFFECTS OF GROWTH-RATE AND MERCURY PARTIAL-PRESSURE ON TWIN FORMATION IN HGCDTE (111) LAYERS GROWN BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

The relationship between twin formation and the growth conditions for (111) HgCdTe epitaxial layers grown by metalorganic chemical vapor deposition was investigated. The existence of twins was confirmed by x-ray diffraction and cross-sectional transmission electron microscopy. The x-ray diffraction intensity of the 180-degrees-0 rotated 422 asymmetric reflection with that of the 422 asymmetric reflection was compared to detect the presence of twins. The layer obtained using a low growth rate and a low Hg partial pressure showed double-positioning (DP) twins. The twins became lamellar as the growth rate increased. Twin-free HgCdTe epitaxial layers were obtained under a high growth rate and a high Hg partial pressure. These results suggest a model for twin formation based on the difference in the growth mechanism of HgTe and CdTe. Twin-free (111) HgCdTe epitaxial layers were reproducibly obtained without using inclined substrates by optimizing the growth conditions by using this model.