Nature of V-shaped defects in HgCdTe epilayers grown by molecular beam epitaxy

The microstructure and micromorphology of V-shaped defects in (3 0 1) and (1 1 2) HgCdTe layers grown by molecular beam epitaxy (MBE) have been investigated in detail on the consecutive stages of its formation by transmission and high-resolution electron microscopy (TEM and HREM) and atomic force microscopy (AFM). The nature of V-shaped defects in epilayers grown by MBE is reported. It was shown that the nucleation of a V-shaped defects occurs on the relief perturbations and its growth is stimulated by non-optimal growth conditions. The formation of V-shaped defect begins from the capture of excess Te along the growth front at the steady-state stages of HgCdTe growth and along the irregularities on the surface of the CdTe buffer layer at the initial stages. High-resolution observations established the occurrence of elemental Te and misoriented HgCdTe grains along the macrosteps on the growth HgCdTe surface. The captured Te initiates the formation of walls with disordered structure (DS walls) extended along the growth direction and containing misoriented HgCdTe grains, Te precipitates and dislocations observed by TEM. While growing, vertical columns packed with stacking faults and bounded by DS walls are formed. We find that these columns can be considered as the basic part of the V-shaped defect in HgCdTe grown by MBE. Due to the continual Te nucleation and twinning inside the defect area, polycrystalline growth can occur.