ARRHENIUS PARAMETERS AND THE COMPENSATION EFFECT IN CRYSTALLIZATION AND DIFFUSION IN AMORPHOUS SI-H(F) IN THE PRESENCE OR ABSENCE OF METAL CONTACTS

A kinetic many-body electron-related model of crystallization in a-Si: H(F) in the presence and absence of metal contacts is proposed. The mo del expresses the parameters of the formation of crystalline nuclei in terms of atomic and electronic material characteristics. The model is based on the kinetic electron-related theory of thermally activated r ate processes in solids. The model considers picosecond atomic and ele ctronic phenomena occurring in the nanometer vicinity of strongly fluc tuating Si atoms executing diffusionlike jumps over energy barriers to more ''ordered'' positions which are associated with the formation of crystalline nuclei. The influence of random picosecond fluctuational beatings (coolings) in the nanometer vicinity of hopping atoms on the nucleation (crystallization) rate is considered. The following main re sults are obtained. (i) The Arrhenius-like equations for the nucleatio n time t(N) linking it with the Si self-diffusion in the metal/semicon ductor interface are found from the kinetic consideration of the cryst allization process, and are in agreement with experimental data. (ii) The Arrhenius activation energy Delta E and the pre-exponential factor to, of the nucleation process are calculated. They are expressed in t erms of local parameters that characterize picosecond atomic and elect ronic processes which occur in the nanometer neighborhood of the hoppi ng Si atoms. (iii) The ''abnormally'' large variations in the prefacto r t(0N) (about 11 orders of magnitude) and the activation energy Delta E (a factor of 7.5) caused by metal contacts are explained. (iv) An e xplanation for a linear dependence between In to, and Delta E found ex perimentally in the crystallization in a-Si:H and a-Si:F is suggested. This dependence is known as the compensation effect (CEF). (v) Coeffi cients in the CEF equation and other kinetic parameters are calculated and expressed in terms of material characteristics, and are in good a greement with experimental data. (vi) An explanation for the large obs erved differences in the rate of nucleation in a-Si:H and a-Si:F is su ggested. (vii) Causes for observed considerable differences in the eff ects of metals not forming and forming silicides on the crystallizatio n are discussed. (viii) Si self-diffusion coefficients are calculated from the nucleation parameters in a-Si:H, a-Si:F and in the metal/a-Si :H(F) interface for the following systems: a-Si:H/Al; a-Si:H/Pd; a-Si: F/Al; and a-Si:F/Pd. (C) 1995 American Institute of Physics.