Optical and transport properties of magnetron-sputtered a-Si:H films doped with erbium

The luminescence properties of erbium-doped silicon offer exciting potential applications in optoelectronics. Although the optical and structural properties of this material have been studied extensively, there have been no prior examinations of the transport properties. In this paper, results from photo-thermal deflection spectroscopy (PDS) and from the study of transient photocurrents (TPC) in rf sputtered a-Si:H films doped with different concentrations of Er are presented. It is shown that films with and without Er feature a broad distribution of localised states. Incorporation of Er does not significantly influence the concentration or energy distribution of shallow states, but increases the sub-gap optical absorption associated with deeper states. The transient photocurrent remains detectable to times of at least 0.1 s, without evidence of significant carrier losses by recombination. This suggests that the transport properties are adequate for electroluminescent device applications.