Experimental Study of Spin-Lattice Relaxation Times in Arsenic-Doped Silicon

Measurements of the spin-lattice relaxation times of arsenic donors in a doped silicon crystal at 8500 gauss and 1.3^∘{}K are reported. The relaxation times for the stable As⁷⁵ were measured by using adiabatic fast-passage techniques to observe the relative amplitudes of the electron resonance signals as a function of time. The relaxation times for the radioactive As⁷⁶ were measured by observing the formation and decay of the nuclear alignment. For the As⁷⁵, of which there are 2.8×{}10¹⁶ atoms/cm³, the direct electron relaxation time is 6.5±{}0.5 minutes and the relaxation time for simultaneous spin-flips of the nucleus and the electron is 4.7±{}1 minutes. For the As⁷⁶, of which there are 3×{}10¹⁰ atoms/cm³, the direct electron relaxation time is 4±{}2 minutes and the relaxation time for simultaneous spin-flips of the nucleus and the electron is {≥}75 minutes.