Ashyphen;deposited undoped microcrystalline silicon (mgr;chyphen;Si:H) has in general a pronouncednhyphen;type behavior. Such a material is therefore often not appropriate for use in devices, such asphyphen;ihyphen;ndiodes, as an active, absorbingilayer or as channel material for thinhyphen;film transistors. In recent work, onphyphen;ihyphen;nsolar cells, this disturbingnhyphen;type character had been successfully compensated by the lsquo;lsquo;microdopingrsquo;rsquo; technique. In the present letter, it is shown that thisnhyphen;type behavior is mainly linked to oxygen impurities; therefore, one can replace the technologically delicate microdoping technique by a purification method, that is much easier to handle. This results in a reduction of oxygen impurities by two orders of magnitude; it has, furthermore a pronounced impact on the electrical properties of mgr;chyphen;Si:H films and on device performance, as well. Additionally, these results prove that the unwanted donorhyphen;like states within mgr;chyphen;Si:H are mainly due to extrinsic impurities and not to structural native defects. copy;1996 American Institute of Physics.
展开▼
