The processes of erbium impurity excitation in Si/Si1−xGex:Er/Si heteroepitaxial structures

Abstract We report a study into the photoluminescence excitation spectra of Er 3+ ions in Si/Si 1− x Ge x :Er/Si heteroepitaxial structures containing 10–31% germanium. The structures of this type are of interest for a laser realization on Si basis. It is shown that a characteristic maximum in the 1040–1050 nm region that appears in these structures is related with the backscattering effects of radiation in the silicon substrate. The excitation efficiency of Er impurity in Si/Si 1− x Ge x :Er/Si structures is investigated in conditions of band-to-band and sub-bandgap optical pumping with the photon energies smaller than the bandgap of a Si 1− x Ge x solid solution. The effective excitation cross-section of erbium ions is shown to depend on the excitation mechanism, the excitation energy, and the parameters of Si 1− x Ge x :Er layers. The values of the effective excitation cross-section of Er 3+ ions in Si/Si 1− x Ge x :Er/Si structures were found to vary from 4 × 10 −15 to 0.5 × 10 −16 cm 2 at T = 77 K. These values are comparable with the highest values obtained for the excitation cross-section of Er 3+ ions in silicon and exceed by several orders of magnitude the effective cross-section of Er 3+ ions under direct (intra-atomic) excitation.