Microstructural transition and degraded opto-electronic properties in amorphous SiGe:H alloys

Abstract

The microstructure of amorphous Si1−xGex:H films with x<0.40 was studied using small-angle x-ray scattering (SAXS) and the results compared with those from opto-electronic and density measurements. The SAXS, the sub-band-gap absorption determined from photothermal deflection spectroscopy, and the photo/dark conductivity ratio all show relatively sharp changes above x=0.2. A corresponding sharp change in the anisotropic character of the SAXS is consistent with a transition to a columnar-like microstructure above x=0.2. The correlated results provide strong evidence for a direct link between degraded opto-electronic properties and the increased heterogeneity associated with the microstructural transition.