Electron Spin Resonance Experiments on Donors in Silicon. III. Investigation of Excited States by the Application of Uniaxial Stress and Their Importance in Relaxation Processes

The excited states of the antimony, phosphorus, and arsenic impurities in silicon have been investigated by subjecting samples to a uniaxial stress and observing the change in the electron spin resonance spectrum. The experiments were performed at 1.25°K and ∼9000 Mc/sec on silicon samples subjected to strains up to ${10}^{-3\mathrm{}}$. From the reduction in the hyperfine splitting and the observed $g$ anisotropy under strain the following results were deduced: For a deformation potential of 11 ev, the valley-orbit splitting (i.e., singlet-doublet spacing) for phosphorus was found to be 0.015 ev, for arsenic 0.023 ev, and for antimony 0.013 ev. For the difference in $g$ values with $H$ parallel ($g_{\mathrm{II}}$) and $H$ perpendicular ($g_{\perp }$) to the valley axis we obtained for phosphorus-doped silicon, $g_{\mathrm{II}}-g_{\perp }=(1.04\mathrm{}\pm 0.04)\times {10}^{-3\mathrm{}}$.

The observed $g$ shifts with strains along different crystallographic directions revealed the presence of two distinct spin-lattice relaxation ($T_s$) mechanisms. These were verified and compared with the theory of Roth and Hasegawa. The effect of applied strains on the mutual electron-nuclear spin flip rate ($T_x$) has been demonstrated. The importance of strain experiments in unravelling relaxation mechanisms is discussed.