Interface Structure and Surface Polarity in CdTe/ZnTe/(112)Si Hetero-Epitaxial System
نویسنده
چکیده
Tellurium adsorption on clean (112) Si surfaces obey a second order kinetic law. The adsorbed Te ad-atoms are highly immobile. Activation energies of adsorption and desorption were measured by isothermal desorption rates. A surface bond energy model was used to calculate the total energy for Te chemisorption on (111) terraces. This model yields a Si-Te bond energy of about 3.46 eV. As-Te bond energy was found to be about 4.0 eV. ZnTe/CdTe epitaxy on Aspassivated Si gave uniform and smooth surfaces. As-pasivated surfaces always produced B-type CdTe crystallographic polarity. Te coverage on As-passivated surfaces were significantly lower than the coverage observed on clean Si surfaces. A ZnTe nucleation model is proposed suggesting an enhancement in Te surface mobility occurs on As-passivated surfaces. ZnTe nucleation on As-passivated surfaces initiates at the step edges. ZnTe/CdTe epitaxy on Teterminated Si and directly on clean (112) Si produced rough surface morphology. The surface polarity type depended on the initial Si surface preparation. A B-type polarity is observed for surfaces treated with Te at temperatures above 500o C. For Te adsorption temperatures below 450o C, CdTe surfaces were A-type and heavily faceted. ZnTe growth on Te-terminated surfaces is suggested to initiate mainly from nucleating on the terraces.
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