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Uniaxial stress dependence of the Orbach spin-lattice relaxation rate of phosphorous and arsenic donors in silicon

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Physical Review B





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The ESR absorption and dispersion signals of P and As donors in silicon have been measured as a function of uniaxial stress with an X-band spectrometer under saturation conditions in the temperature range between 12 and 20 K, where the spin-lattice relaxation rate 1T1 is dominated by the Orbach process. The results have confirmed a suggestion by Abragam that uniaxial stress should produce a substantial decrease in the shallow-donor Orbach relaxation rate. These experiments support the hypothesis that the impurity spin-orbit interaction within the 1S-T2 manifold is the Orbach spin-flipping mechanism and point to the importance of the 1S-T2 level width in the relaxation process for P and As donors. Experiments have been performed for both longitudinal (F' H') and transverse (F' H') geometries with the compressive force F' applied along the [100], [110], and [111] axes. Qualitative features of the data include: (i) 1T1 decreases to about 20% of its zero stress value for F' [100] axis; (ii) a very small change in 1T1 is observed for F' [111], (iii) a minimum in 1T1 versus stress, followed by a very gradual rise in 1T1 versus stress is observed for certain geometries; (iv) a dependence of 1T1 on magnetic field direction is observed for the transverse case (F' H') for a large constant [110] stress. It is demonstrated that all four of these effects are predicted by the valley-repopulation model involving only the 1S-T2 states for the Orbach relaxation rate. © 1978 The American Physical Society.

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