Investigation of strain relaxation in short-period Si m Ge n superlattices using reciprocal space mapping

Abstract

The optoelectronic properties of ultrathin Si<SUB>m</SUB>Ge<SUB>n</SUB> strained layer superlattices (SLSs) depend strongly on their structural perfection and the strain adjustment of the SLS by a Si<SUB>1-x</SUB>Ge<SUB>x</SUB> alloy buffer. We used double crystal and triple axis x-ray diffractometry to characterize the structural properties of short period Si<SUB>6</SUB>Ge<SUB>4</SUB> and Si<SUB>9</SUB>Ge<SUB>6</SUB> SLSs grown on about 1 micrometers thick step-graded SiGe alloy buffers. As grown SLSs and samples annealed subsequently at 550 degree(s)C, 650 degree(s)C, and 780 degree(s)C for 60 min were investigated, the latter to study effects of post-growth thermal treatments typical for conventional Si device fabrication. Precise strain data were extracted from two-dimensional reciprocal space maps around (004) and (224) reciprocal lattice points. These data were used as refined input parameters for the dynamical simulation of the integrated intensity along the q[004] direction.