Photoluminescence excitation spectroscopy of erbium in epitaxially grown Si:Er structures

Excitation of erbium photoluminescence in Si:Er epitaxial structures has been studied within a broad pump wavelength range (λex = 780-1500 nm). In all the investigated structures considerable signal of the 1.5 μm erbium photoluminescence has been observed at pump photon energies well below the silicon band-gap value (λex > 1060 nm) where seemingly no exciton generation occurs. Possible mechanism of erbium ion excitation in silicon without participation of excitons is discussed.