Dangling-bond states in a SiGe:H,F measured by temperature-dependent mu tau

The authors report a novel technique for measuring the density distribution of the D/sup 0/-/ state in a-Si:H before and after light soaking and in a-SiGe:H,F alloys for solar cells. Electron time-of-flight (TOF) measurements as a function of temperature form the basis of this technique. The deep trapping of electrons controls the mobility-lifetime product ( mu tau )/sub n/, which is evaluated from the integrated TOF current. The dominant deep trap is the D/sup 0/-/ level. The authors determine the density of D/sup 0/-/ states in a:SiGe:H,F that peak at SiE/sub c/-(0.40 to 0.45) eV with maxima in the 10/sup 18/ to 10/sup 19/-cm/sup -3/ eV/sup -1/ range. In a-Si:H, the peak lies at E/sub c/-0.45 eV; it is observed to grow with increasing light-soaking time.<
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