Characteristics of the low energy photoluminescence in μc-Si films

The temperature and excitation-intensity dependence of the ∼0.9 eV photoluminescence (PL) band has been studied in several microcrystalline silicon (μc-Si) films with varied crystallinity. When the measurement temperature is increased from 15 to 180 K, the PL peak energy redshifts from 1.0 to 0.83 eV. The PL quenching of the intensity follows a model of carrier thermalization in an exponential band tail with a width of ∼20 meV. The total PL intensity (IPL) as a function of excitation intensity (Iex) obeys a power law of IPL∝IγeX, where γ≈0.65 or 1 for high or low excitation intensity, respectively. The experimental results suggest that the ∼0.9 eV PL band originates from radiative tail-to-tail transitions in the grain-boundary region in μc-Si