New deep level luminescence bands observed from both a SiGe alloy layer and Si/Ge superlattice structures

Abstract

Photoluminescence measurements have been made on Si/Ge short period superlattice structures grown on a SiGe alloy buffer layer and on a similar SiGe alloy layer without a superlattice. Using an InSb detector with a low energy cutoff at ∼450 meV, the major luminescence features observed were two broad bands with maximum intensities at ∼530 and ∼720 meV. The luminescence intensity was found to vary with the superlattice composition but was substantially stronger for the SiGe alloy layer without a superlattice. We ascribe these luminescence features to defects in the SiGe alloy layers. This is supported by the observation that the introduction of deliberate copper contamination at 600 °C dramatically increases the photoluminescence signal.