Relaxation of the shallow acceptor center magnetic moment in a highly doped silicon

Results on the temperature dependence of the residual polarization of negative muons in crystalline silicon with germanium, boron and phosphorus impurities are presented. The measurements were carried out in a magnetic field of 0.1 T transverse to the direction of the muon spin in the temperature range 4.2-300 K. It is found that in a silicon sample with a high concentration of germanium impurity (9·1019 cm-3), as in the samples of n- and p-type silicon with impurity concentrations up to ∼1017 cm-3, the relaxation rate ν of the magnetic moment of the μAl-acceptor depends on temperature as ν∼Tq, q∼3 at T=(5-30) K. For the samples of degenerate silicon the absolute values of the relaxation rate increase and its temperature dependence becomes weaker in the same temperature range. On the basis of the experimental data it is concluded that for a degenerate silicon at T≤30 K the relaxation of the acceptor center magnetic moment is determined by the spin-exchange scattering of free charge carriers on the acceptor. The estimates for the effective cross-sections of spin-exchange scattering of holes and electrons on the Al-acceptor in Si are obtained. (author)