Characterization of semiconductor strained layers grown on (110)-type substrates by high-resolution X-ray diffractometry

Abstract

We present an analytical approach to determine the strain and composition in simple epitaxial films, superlattices and multiple quantum wells grown on (110) substrates by means of the high-resolution X-ray rocking curve technique. Peak separations between the substrate and the epilayer are used from suitable reflections to calculate the lattice parameters in the epilayer using simple equations, followed by a calculation of the layer strain and composition based on the linear elasticity theory. Two independent reflections are sufficient to fully characterize SiGe layers grown on Si, if no tilts relative to the substrate are present, whereas most compound semiconductors may require additional rocking curves to account for the layer tilt. The effect of film thickness on the calculations is examined, and a procedure to correct for the deviation from Vegard's law in SiGe is formulated. The technique is demonstrated for an SiGe multiple quantum well grown on an Si(110) substrate.