Cascade Phonon-Assisted Trapping of Positrons by Divacancies in n-FZ-Si(P) Single Crystals Irradiated with 15 MeV Protons

The trapping of positrons by the radiation defects in moderately doped oxygen-lean n-FZ-Si(P) single crystal irradiated with 15 MeV protons has been investigated in a comparative way using the positron lifetime spectroscopy and Hall effect measurements. The experiments were carried out within a wide temperature interval ranging from 25 K - 29 K to 300 K. The positron trapping rate for divacancies was reconstructed in the course of many-stage isochronal annealing. The concentration and the charged states of divacancies (V-2(-) and V-2(--)) were estimated. The temperature dependency of the trapping cross section of positrons by the negatively charged divacancies is in a good agreement with the data of calculations based on the assumptions of the cascade phonon-assisted mechanism of exchange of the energy between the positron and acoustic long-wave phonons. Obeying similar to T-3 law, the cross-section of the trapping of positrons by divacancies changes considerably ranging from similar to 1.7x10(-12) cm(2) (66 - 100 K) to similar to 2x10(-14) cm(2) (approximate to 250 K). The characteristic length of trapping of the positron by V-2(--) divacancy was estimated to be l(0) (V-2(--)) approximate to (3.4 +/- 0.2) x10(-8) cm.