Photoluminescence Of Sisnc Alloys Grown On (100) Si Substrates

Abstract

AbstractPhotoluminescence (PL) of SiSnC alloys grown on Si (100) substrate by molecular beam epitaxy (MBE) has been investigated. The following epitaxial layers were investigated. The samples were similar in structure, and consisted of a 200 Å Si buffer layer grown on a (100) Si substrate followed by the respective alloy layer; a 4500 Å Si0.955Sn0.03C0.015, a 1500 Å Si0.9Sn0.04, or a 1500 Å Si0.985C0.015. The layer composition was measured by Rutherford back scattering spectrometry (RBS) and confirmed by x-ray diffraction analysis (XRD). X-ray diffraction measurements of the layers confirmed the Sn and C were substitutional and the layers were pseudomorphic and coherently strained. The Si0.955Sn0.03C0.015 alloy layer was found to be strain compensated. PL spectra of all the layers revealed band edge luminescence as well as a very sharp peak at 0.767 eV superimposed on a very broad peak that exhibited excitonic behavior. The addition of C to the alloys resulted in a reduction of the bandgap, contrary to what is predicted by Vegard's Law. However, the addition of Sn results in a reduction in the bandgap, which was attributed to the bulk alloy effect and residual strain. The luminescence feature at 0.767 eV was found to be much more intense in alloys that contain carbon. We have observed quite similar deep-level well resolved PL spectra for SiGe, SiC, SiSn, SiGeC, SiSnC, and SiGeSnC alloy layers grown by MBE on Si (100) substrates. Previous studies on PL of silicon have reported a peak at 0.767 eV to be associated with oxygen (P line) and the broad peak to carbon/oxygen complexes.