Limiting factor of defect-engineered spin-filtering effect at room temperature

Abstract

We identify hyperfine-induced electron and nuclear spin cross-relaxation as the dominant physical mechanism for the longitudinal electron spin relaxation time $\left({T}_{1}\right)$ of the spin-filtering $G{a}_{i}^{2+}$ defects in GaNAs alloys. This conclusion is based on our experimental findings that ${T}_{1}$ is insensitive to temperature over 4--300 K, and its exact value is directly correlated with the hyperfine coupling strength of the defects that varies between different configurations of the $G{a}_{i}^{2+}$ defects present in the alloys. These results thus provide a guideline for further improvements of the spin-filtering efficiency by optimizing growth and processing conditions to preferably incorporate the $G{a}_{i}^{2+}$ defects with a weak hyperfine interaction and by searching for new spin-filtering defects with zero nuclear spin.