Electronic properties of amorphous and microcrystalline silicon prepared in a microwave plasma from SiF4

Abstract

Abstract The paper is concerned with a systematic investigation of electronic, optical and structural properties of hydrogenated Si films prepared by decomposing a mixture of SiF4, H2 and (initially) Ar in a microwave plasma (2·45 GHz). The temperature dependence of the dark conductivity and drift mobility, as well as measurements of photoconductivity, H content, optical absorption and electron diffraction have been used to characterize the specimens. Two related reactor geometries were studied. The first, system A, included the coaxial tube arrangement for gas flow through the cavity also used by Shibata et al. The electronic quality of the initial material was greatly improved by two modifications: firstly removal of the inner tube to allow interaction of the SiF4, and H2 in the cavity and secondly exclusion of the Ar in the mixture to prevent defects from Ar-ion bombardment. With this arrangement, system B, good electronic properties were obtained (nμτ≈10−5 cm2 V−1). System B results show a transition ...