Diffusion Lengths in a-Si:H/a-Sic:H and a-Si:H/a-Sige:H Multilayers Determined by the Grating Method

Abstract

ABSTRACTThe technique of the steady-state photocarrier grating (SSPG) has been applied to different series of a-Si:H/a-Si1-xCx:H and a-Si:H/a-Si1-xGex:H Multilayers. In dependence on the electronic well and barrier widths of the Multilayers, characteristic changes of the measured ambipolar diffusion lengths Lambi have been found. The general trend of Lambi can be understood in terms of interface recombination and scattering, when the mean composition of the multilayers is kept constant. In some cases, values of Lambi of multilayers were higher than the corresponding value of a homogeneous a-Si:H reference layer, a fact which might be explained by a dimensional effect. The effect in a-Si:H/a-Si1-xCx:H Multilayers was reduced with green HeNe-laser illumination with photon energies above the Taue gap of the barrier Material, instead of a red illumination generating photocarriers only in the potential wells.