APPLICATIONS OF VARIABLE-ANGLE SPECTROSCOPIC ELLIPSOMETRY TO STRAINEDSIGE ALLOY HETEROSTRUCTURES

Variable angle spectroscopic ellipsometry (VASE) has been used to char acterize several SixGel-x/Ge heterostructures. First, SixGel-x/ Ge sup erlattice (SL) structures were characterized in terms of the layer thi cknesses, composition, x, of the SixGel-x layer, and oxide thickness. High-resolution X-ray diffraction results are also presented for the S ixGex-l/Ge SL structures and are shown to be in close agreement with t he VASE results once strain effects are taken into account. VASE has a lso been used to study thick, Ge-rich SixGel-x/Ge heterostructures tha t have been grown on Si substrates. A stepped buffer has been deposite d first in order to minimize the strain in the SixGel-x/Ge layers, VAS E can be used to give a qualitative determination of the residual stra in along with the thickness of all layers within the optical penetrati on depth from the surface.