Structural and optoelectronic properties of microcrystalline silicon germanium

Abstract The structural and optoelectronic properties of μc-Si 1− x Ge x :H alloys prepared by plasma enhanced chemical vapor deposition (PECVD) were investigated as a function of the deposition parameters germane concentration and hydrogen dilution. With decreasing hydrogen dilution we found a transition from microcrystalline to amorphous growth, which shifts to higher hydrogen dilution if the germanium concentration is enhanced. Additionally, we observed different built-in coefficients of germanium in the amorphous and crystalline phase. We correlate these structural properties with the optoelectronic properties. While the dark conductivity is only weakly affected by the germanium concentration, it decreases strongly upon a decrease of hydrogen dilution. Although the optical absorption increases with rising germanium the photoconductivity decreases indicating an increase of the defect density.