Generation and dissociation of complexes of iron and phosphorus atoms in silicon

To examine the possibility of generating complexes of iron and phosphorus atoms in silicon, neutral interstitial iron in phosphorus doped silicon crystals with various concentrations were measured with the electron spin resonance (ESR) method after cooling from high temperature at various cooling rates. This concentration was found to depend on the cooling rate when the concentration of phosphorus was high: The concentration of interstitial iron was low only when the concentration of phosphorus was high and the cooling rate was slow. This result shows that some iron atoms form complexes with phosphorus atoms during cooling and become ESR-inactive. Annealing behaviors of these complexes monitored as to the concentration of neutral interstitial iron are described as a combination of two processes, namely, the release of iron atoms from iron-phosphorus complexes and the diffusion of iron to quenched-in defects which are concluded to exist based on the dependence of annealing behavior on the cooling rate. From the analysis of annealing behaviors, the binding energy between iron and phosphorus atoms and the activation energy of diffusion of iron were determined to be 0.90 and 0.80 eV, respectively.