Photoluminescence in a‐Si1−xCx:H films

A study of steady‐state and time‐resolved photoluminescence (PL) and optical properties of a‐Si1–xCx: H‐films prepared by glow‐discharge decomposition of gas mixtures of SiH4 and CH4 is presented. With increasing carbon content x the PL‐spectra shift to higher energies and broaden considerably. Simultaneously the quantum efficiency decreases at low x but increases again above x ≈ 0.6. The PL‐decay after pulse excitation (10 ns) is enhanced with increasing x, the lifetime spectra shift to shorter times by more than two orders of magnitude (x < 0.45). The data indicate a strong decrease of the average radiative lifetime with x. This behavior is explained by an enhancement of the Coulomb attraction between the recombining carriers and/or faster thermalization in the band tails.