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

We identify hyperfine-induced electron and nuclear spin cross-relaxation as the dominant physical mechanism for the longitudinal electron spin relaxation time (T sub(1)) of the spin-filtering Ga super(2+) i defects in GaNAs alloys. This conclusion is based on our experimental findings that T sub(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 Ga super(2+) i 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 Ga super(2+) i defects with a weak hyperfine interaction and by searching for new spin-filtering defects with zero nuclear spin.