UHV-CVD growth and annealing of thin fully relaxed Ge films on (001)Si

The structural effects of single and cyclic thermal annealings on relaxed Ge epilayers on Si(0 0 1) are investigated. The structural morphology of the films is studied ex situ by Rutherford back scattering spectrometry in channelling geometry (RBS-C), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The effects on optical properties are demonstrated by optical transmission spectroscopy. Thermal cycles between 750 and 870 °C were found to be efficient for reducing the threading dislocations density. But, in return for it, thermal cycles result in a strong interdiffusion and a high disorder at the Ge/Si interface, as shown through a χmin value of 14.4%. On the contrary, a single annealing at 720 °C decreases the density of dislocations but does not induce any new disorder. Moreover, the single annealing does not alter the near-IR optical absorption of the Ge layer.