Excitation spectroscopy of photoluminescence in a-Si:H

The photoluminescence (PL) excitation spectrum (intensity of PL as a function of the wavelength of the exciting light) has been measured over the range 1.0 – 1.25 eV for PL at 0.79 eV using a free electron laser (FEL) as the excitation source. At all wavelengths, the PL intensity varies with incident laser power, I, as I0.9 independent of wavelength. The resulting PL excitation spectrum has two distinguishing features, an exponential rise at lower energies followed by a leveling-off above about 1.15 eV. Although the precise functional form of the data at low energies is not uniquely determined, the data are consistent with an exponential rise whose slope is the same as that measured in optical absorption at higher energies.