Photoluminescence Characterization of SiGe Grown on Si(001)

This paper presents our recent experimental work on photoluminescence (PL) characterization of strain-relaxed uniform composition Si1-xGe layers with 0.17 < x < 0.34 grown step-wise graded buffer on Si(100) by ultra-high vacuum chemical vapor deposition (UHV/CVD). Near band edge radiative recombination at low temperature is dominated by non-phonon assisted excitons and biexcitons confined in three dimensional potential wells (Ge-rich region) created by alloy fluctuations. Strain relaxation in Si1-xGex layers during the epitaxial layer growth produces a threading dislocation network. This network produces well-resolved four D lines in the measured PL spectra. Variations of the intensity and peak position of the four D lines as a function of post-growth annealing temperature are observed. We propose that a local re-arrangement of atoms near the dislocation is responsible for the re-distribution of the deep electronic states with the band gap.