Untersuchungen an Si-Epitaxieschichten auf Mg-Al-Spinell-Einkristallen

In Verneuil-grown MgAl-Spinels etch pit densities with non-uniform distribution between 10⁴ and 10⁷ cm⁻² were found. X-ray measuements of orientations showed deviations of the growth direction from the rod axis up to 8 deg. Berg-Barrett photographs point to distinctly marked substructures. Si epitaxial layers on MgAl-spinel were prepared according to the pyrolytic reductive reaction of SiCl₄ in H₂. Nucleation, etching reaction on the substrate and the quality of the Si layers are discussed. Measurements of the carrier mobility in the doping range from 10¹⁶ to 10¹⁷ · cm⁻³ resulted in 60 to 80 p.c. of the volume mobility of the silicon. Problems of segregation with annealing are dealt with. The use of Si layers on insolating substrates is discussed.