Structural and electrical properties of Co-doped β-FeSi2 thin films prepared by RF magnetron sputtering

(220)- and (422)-oriented Co-doped n-type β-FeSi2 films were formed onto p-type Si (100) by radio frequency (RF) magnetron sputtering using a FeSi2 target which placed square Co chips and by subsequent annealing at 900°C for 20h. The effects of annealing time (ta) and Co-doping on crystal structures and electrical properties were investigated by X-ray diffraction (XRD), Hall and current-voltage (I-V) measurements. The ta dependence showed that all the annealed un-doped β-FeSi2 films exhibited n-type conductivity with electron concentration of 2 × 1016 - 7× 1016cm-3, while the Co-doping dependence showed that n-type β-FeSi2 films with electron concentrations ranging from 1016 to 1020cm-3 were successfully formed. I-V characteristics of n-β-FeSi2/p-Si demonstrated rectifying properties showing a decrease in reverse-bias current with increasing ta, which can be explained by an improvement of crystalline quality of β-FeSi2 films as evidenced by XRD. I-V characteristics of Co-doped n-β-FeSi2/p-Si diodes also revealed an increase in current under forward and reverse bias, which can be caused by an increase in minority electron concentration in p-Si and by an increase in generation-recombination current at the depletion layer.