Recombination of mobile carriers across boron excited levels in silicon at low temperatures

Carrier recombination through shallow boron-impurity centers in doped weakly compensated silicon is studied. Much attention is paid to theoretical explanation of the “empirical” temperature dependences of the carrier lifetime $\tau(T)$ in the temperature range of (1.7–4.2) K at the doping level $n_{\mathrm{B}}\ge$ 10$^{14}$ cm$^{-3}$ and compensation $\le$ 10% ($n_d+n_a\le$ 10$^{13}$ cm$^{-3}$). It is possible to rather accurately determine that the shallow excited level with a binding energy of 5 meV (3$s$-state) is quasi-resonant. Approximate formulas for the trapping efficiency are obtained. The effect of “weak” magnetic field (10$^2$–10$^3$) G on the capture coefficient is studied; it is shown that the “weak” magnetic field slightly reduces the lifetime of carriers, thus stimulating their recombination.