ELECTRONIC AND OPTICAL-PROPERTIES OF HOT-WIRE-DEPOSITED MICROCRYSTALLINE SILICON

We conducted a study on undoped and doped hydrogenated microcrystallin e silicon (mu c-Si) samples deposited by hot-wire chemical vapor depos ition for determination of the structural, electronic and optical prop erties. Light scattering, investigated by total and specular transmiss ion and reflection, as well as angular resolved measurements, results mainly from the surface but with an intrinsic contribution from the in terior. The optical properties resemble that of monocrystalline Si: th e refractive index in the visible, the reflectance peaks in the near u ltraviolet which may only appear after surface polishing, and the abso rption coefficient which is larger than in monocrystalline silicon and varies with sample thicknesses. Depending on the doping level, the da rk conductivity prefactor and activation energy exhibit either normal or anti-Meyer-Neldel rule behavior. The mobility-lifetime product from steady state photoconductivity strongly depends on the position of th e Fermi energy with a minimum for low p-type doping, suggesting the im portance of information on the Fermi energy if the mobility-lifetime p roduct is given as an indicator for material quality of microcrystalli ne Si. (C) 1998 Elsevier Science B.V. All rights reserved.