Nucleation of ZnTe/CdTe epitaxy on high-Miller-index Si surfaces

Tellurium-adsorption studies were conducted on {111}-type Si surfaces that are off-cut from the {111} in the range of 0-30degrees on both nonpassivated- and arsenic-passivated Si surfaces. Relative surface coverages as a function of Te exposure time and Si-surface orientation were obtained with in-situ x-ray photoelectron spectroscopy (XPS). The XPS results indicate that Te coverage on arsenic-passivated Si surfaces increases as the step density of the surface increases. In contrast, Te-adsorption studies conducted on nonpassivated-Si surfaces showed no dependence between TO coverage and the surface-step density. Subsequent ZnTe and CdTe molecular-beam epitaxial growth on these high-Miller-index Si surfaces further validate a step-edge nucleation model. Additionally, it was observed that the CdTe-epilayer orientation did not always reproduce the Si-substrate orientation and was a function of both the initial Si surface and the growth conditions used.