Spin-Lattice Relaxation of Shallow Donors in Heavily Doped Si

Abstract

A theory is proposed to explain the dependence of spin-lattice relaxation rate, 1⁄T_s, of donors on the concentration and the degree of compensation. In the theory donor electrons are classified into two groups according to their spin-lattice relaxation rate being rapid or slow. The first is those electrons belonging to the close pairs of phosphorus atoms which are few in number. One site of a close pair is occupied and the other occupied. These electrons relax rapidly through the hopping motion accompanied by reversal of spin orientation. The second group is those electrons associated with the isolated phosphorus atoms. They approach to the first group via the hopping motion without changing their spin orientations and finally relax at the sites of the fast-relaxing centers associated with the first group. Qualitative agreement between calculation and the experimental data of Igo is obtained with the exception of the heavily compensated samples.