CONCENTRATION DEPENDENT SPIN-LATTICE RELAXATION IN N-TYPE SILICON

Spin-lattice relaxation mechanisms for the donor electrons in uncompensated silicon are presented. Major isolated spins transfer their excitation energies via the spin-diffusion process to the fast-relaxing centers. For lightly doped samples. Nd ≲ 1016cm3, exchange-coupled donor pairs act as the fast-relaxing centers. Theory provides the correct order of magnitude for the relaxation rate 1 Ts. However, the calculated relaxation rate 1 Ts, for this process is field independent, while the observed rate shows a weak field dependence. For more heavily doped samples, Nd > 1016/cm3, the relaxation rate can be explained by assuming the presence of a small concentration of neutral-ionized donor pairs. The relaxation process for these pairs is the resultant of two different mechanisms, a field dependent mechanism and a field independent one. The former depends strongly on the donor concentration and the latter shows relatively weak dependence on Nd. © 1968.