Simulation of the spin polarization and the charge transport in Zener tunnel junctions based on ferromagnetic GaAs and ZnO

Simulations of the tunneling current as a function of voltage for a Zener diode where both sides are ferromagnetic have been performed. The current is evaluated as a function of the voltage and of the magnetization on each side of the diode. Calculations are made using an in-house developed simulator which solves the Poisson, electron and hole continuity equations self-consistently. The drift-diffusion model is used to calculate the charge carrier distribution. The current expressions were modified to consider degenerate semiconductors. Our simulator includes a non-local tunneling transport model which was modified to account for the spin polarization of the carriers. The tunneling magnetoresistance is obtained from the I–V characteristics for parallel and antiparallel configurations of the magnetization vectors in each side of the device. Two different devices were analyzed, one that corresponds to Mn-doped GaAs in which the ferromagnetism is stronger on the p side of the diode, and the other that corresponds to ZnO where there are likely to be many more carriers on the n side of the diode. We found good agreement between the results of our simulations and the theoretical predictions of the tunneling magnetoresistance, especially at room temperature. We also found that larger bandgap materials show larger tunneling current but lower tunnel magnetoresistance.

keywords: Magnetoelectronics, Spintronics, Spin-polarized transport in semiconductors, Junction diodes, Tunneling, III–V semiconductors, II–VI semiconductors