Physical mechanism for thermal activation of electron spin filtering and spin generation in InAs/GaAs nanostructures

Recently we succeeded in generating record-high conduction electron spin polarization (exceeding 90%) at room temperature (RT) in InAs/GaAs quantum dots (QDs) [1]. This was accomplished by defect-engineered remote spin filtering via an adjacent tunneling-coupled GaNAs spin filter. Opposite to the general trend seen in other approaches, the spin polarization generated by our approach is found to increase with increasing temperature up to RT, desirable for practical device applications in spintronics. In this work we show that this increase originates from a thermally accelerated remote spin-filtering effect as a result of thermally activated spin-dependent recombination via the spin-polarized spin-filtering defects, i.e., grown-in Ga self-interstitials, which selectively deplete conduction electrons with an opposite spin orientation to that of the defect electron. This conclusion is based on our experimental evidence for a direct correlation between the measured spin polarization degree and the defect-mediated non-radiative recombination efficiency over a wide temperature range, which is further supported by a detailed rate equation analysis of the spin and recombination dynamics.



[1] Y. Huang, V. Polojärvi, S. Hiura, P. Höjer, A. Aho, R. Isoaho, T. Hakkarainen, M. Guina, S. Sato, J. Takayama, A. Murayama, I.A. Buyanova and W.M. Chen, Nature Photonics 15, 475 (2021).