Photoluminescence of microcrystalline silicon at low temperatures

Abstract

Photoluminescence (PL) from semiconductors can be related with the quasi-Fermi level splitting of the electron-holeensemble from which the radiation originates. For the interpretation of the temperature-dependent c-Si:H PL Planck's generalized law is extended and applied to describe the radiative recombination via band-tail states. This substantial refinement of existing approaches allows for the modeling of temperaturedependent spectra over the entire measured temperature range and furthermore provides access to the quasi-Fermi level splitting (qFL) of electron-hole ensembles in the thin film and furthermore yields quantitative information on band-tail energies. In crystalline silicon, an increase in the quasi-Fermi level splitting causes only an increase in the overall PL-intensity, while the spectral shape of the spectrum is unaffected. In contrast, the PL-spectra of c-Si:H differ with varying qFL-splitting both in intensity and shape. Only by introducing variations of qFL-splitting and constructing an overall PL-spectrum that is a superposition from excitation states with different qFLsplittings, the experimental temperature-dependent PL spectra from c-Si:H can be reconstructed for the entire temperature range.Temperature-dependent PL spectra of c-Si:H silicon (symbols) and fits according to our proposed model (lines).