Morphology and crystallinity of homoepitaxial (100)ZnTe: interplay between ad-atom stoichiometry and defects nucleation during MOVPE

The morphology and structure of metalorganic vapour phase epitaxy grown homoepitaxial (1 0 0)ZnTe layers on high-quality substrates grown by the vertical gradient freezing method is reported. Growth below 350 °C leads to surface ridging along a ?1 1 0? in-plane direction of the epilayer, the morphology of samples grown at or above 350 °C depending instead on the Te:Zn ad-atom relative abundance. Nearly featureless morphology is observed for epilayers grown under Zn-rich or nearly stoichiometric surface conditions, whereas large pyramid-like hillocks develop on Te-rich surfaces, their density reaching up to 106-107 cm-2. Hillock formation is supposed to be driven by Te ad-atoms experiencing a Schwoebel potential barrier at the step edges around spiral centres, the latter ascribed to partial dislocation pairs bounding stacking faults (SFs). Analysis of the X-ray diffuse scattering intensity around the (4 0 0) reciprocal lattice point of the samples demonstrates that SFs occur in epilayers grown at or above 350 °C, their density increasing with the growth temperature. The SF average diameter on {1 1 1} planes is estimated as ~200-300 nm.