Suppressing spectral diffusion in phosphorus-doped silicon via optical excitation in high magnetic fields*

The phosphorus donor impurity in silicon is a promising candidate for spin-based quantum devices. Recent experiments have shown that above-band gap optical excitation can result in strong hyperpolarization of the donor nuclear spins [1,2]. Here we show that low-power above-band-gap excitation can also extend the phase memory time of the donor electron spins in a low-concentration (∼3.3 - 3.5 × 10¹⁵ cm^-3) phosphorus-doped natural abundance silicon sample. A two-pulse Hahn echo experiment at 8.5T and 4K was used to measure the decay of the echo amplitude with time. The non-exponential decays (∼exp(-(t/T_SD)ⁿ) suggest that the phase memory time is dominated by spectral diffusion due to the ²⁹Si spins [3]. T_SD was measured to be 110 µs in the dark and with sub-bandgap excitation, rising to over 180 µs with 1050 nm laser excitation. With 980 nm excitation, T_SD was observed to increase with applied laser power, saturating at 200 µs.
[1] D. R. McCamey et al.,Phys. Rev. Lett. 102, 027601 (2009).
[2] P. Gumann et al., Phys. Rev. Lett., 113, 267604 (2014).
[3] A. M. Tyryshkin et al.J Phys-Condens Mat., 18, S783–S794 (2006).