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

Abstract

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 con- centration 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 sam- ples of degenerate silicon in the given temperature range. Based on the experimental data obtained, the conclu- sion 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 acceptor Al center in Si: σ h ~ 10 -13 cm 2 and σ e ~ 8 × 10 -15 cm 2 at the acceptor (donor) impurity concentration na(nd) ~ 4 × 10 18 cm -3 . © 2001 MAIK "Nauka/Interperiodica".