NANOSTRUCTURED GE DISTRIBUTION IN A-SIGE - H-ALLOYS FROM ANOMALOUS SMALL-ANGLE X-RAY-SCATTERING STUDIES

The nanostructures of hydrogenated amorphous silicon germanium alloys, a-Si1 - xGex:H (x similar to 0.5 to 0.7), prepared by different plasm a enhanced chemical vapor deposition techniques, are examined by anoma lous small-angle X-ray scattering (ASAXS). Clear evidence of inhomogen eous distributions of Ge are found with correlation lengths of 1.0 to 1.4 nn. This non-uniformity is removed by enhanced ion bombardment dur ing growth and it is reduced by hydrogen dilution of the plasma. These more homogeneous materials result in improved photovoltaic and opto-e lectronic performance. The anisotropic ASAXS from the Ge is consistent with Ge enrichment along columnar-like nanostructures. (C) 1998 Elsev ier Science Ltd. All rights reserved.