Spontaneous spin-filter effect across EuS/GaAs heterojunction

摘要

We study current transport across a EuS/GaAs heterojunction (HJ) modulated by the filtering action of the ferromagnetic semiconductor EuS in zero external magnetic field. Analysis of the current-voltage (I-V) characteristics of the current injected from EuS into GaAs across the HJ yields a value for the Zeeman splitting of the EuS conduction band of (0.48 ± 0.12) eV at 5 K. The change in the barrier height at the HJ mimics the change of the spontaneous magnetization of EuS, i.e., it has Brillouin like characteristics with a T_C of 17 K. Utilizing the experimentally obtained values for the Zeeman splitting as input parameters, we analyze the I-V characteristics for unpolarized electrons injected from GaAs, to estimate the polarization detection efficiency as a function of bias and temperature below 30 K.