THE REACTION-KINETICS OF IRON-BORON PAIR FORMATION AND DISSOCIATION IN P-TYPE SILICON

The reaction kinetics of iron-boron formation and dissociation in p-type silicon were investigated. The results indicate that the reaction kinetics depend strongly on the relative position of the ionization energy of interstitial iron and the Fermi level. At temperatures below a transition temperature where the ionization energy of interstitial iron is equal to the Fermi level, the iron-boron pairing reaction is dominated by the electrostatically enhanced recombination process between interstitial iron and substitutional boron. This pairing reaction is limited to the iron diffusion which may be described by the diffusion coefficient correlated by Weber.8 At temperatures above the transition temperature, the concentrations of ionized and neutrally charged interstitial iron species are in equilibrium. The equilibrium reaction, which is facilitated by thermally excited electrons, gives rise to a deionization of the charged interstitial iron species and in turn causes the dissociation of the iron-boron pairs.