Magnetic moment relaxation of a shallow acceptor center in heavily doped silicon

Results of studying the temperature dependence of the residual polarization of negative muons in crystalline silicon with germanium (9×10 19 cm −3 ) and boron (4.1×10 18 , 1.34×10 19 , and 4.9×10 19 cm −3 ) impurities are presented. It is found that, similarly to n-and p-type silicon samples with impurity concentrations up to ∼10 17 cm −3 , the relaxation rate ν of the magnetic moment of a μ Al acceptor in silicon with a high impurity concentration of germanium (9×10 19 cm −3 ) depends on temperature as ν∼T q , q≈3 at T=(5–30) K. An increase in the absolute value of the relaxation rate and a weakening of its temperature dependence are observed in samples of degenerate silicon in the given temperature range. Based on the experimental data obtained, the conclusion is made that the spin-exchange scattering of free charge carriers makes a significant contribution to the magnetic moment relaxation of a shallow acceptor center in degenerate silicon at T≲30 K. Estimates are obtained for the effective cross section of the spin-exchange scattering of holes (σ h ) and electrons (σ e ) from an Al acceptor center in Si: σ h ∼10−13 cm2 and σ e ∼8×10−15 cm2 at the acceptor (donor) impurity concentration n a (n d )∼4×1018 cm−3.