Defect Evaluation of Heavily P-Doped Si Epitaxial Films Grown at Low Temperature

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Abstract
Heavily P-doped epitaxial Si films with carrier concentration of 3×1021 cm-3 have been successfully grown by plasma chemical vapor deposition using a gas mixture of SiH4, SiF4, H2 and PH3 at a very low temperature of 250°C. From the annealing characteristics of heavily P-doped Si films, it was found that the electron concentration decreased once after annealing at 600°C but increased subsequently upon raising the annealing temperature. The possibility of the formation of a vacancy-type defect complex, typically (v-P4), a vacancy surrounded by four phosphorus atoms, was proposed to interpret this phenomenon. Furthermore, a positron annihilation experiment was employed to investigate this vacancy-type defect in Si films and good agreement was obtained between thermodynamical calculation based on the v-P4 model and the positron annihilation experiment.