Transport properties of a spin polarizer for electrons

Abstract We describe the transport properties of a Ga 1 - y Al y As / Ga 1 - x Mn x As resonant tunneling diode (RTD). In previous works we have studied the transport of holes at the valence band (VB), considering the contacts made of GaAs:Be (p-doped). We now focus on electron transport as it is known that the spin coherence length for electrons is much larger than for holes. Therefore, we now consider the contacts made of GaAs:Si (n-doped). Ga 1 - x Mn x As is a diluted magnetic semiconductor (DMS) of p type in which the ferromagnetism produces a spin splitting of the VB and the conduction band (CB) due to the s,p–d exchange interaction. The splitting of the CB generates a spin splitting of the energies associated with electron resonant peaks in the well. We apply a variable bias between the emitter and the collector. As the spin degeneracy is lifted and the current flows through the resonant peaks, we get a spin polarized current when only one of these peaks is in between the Fermi level and the bottom of the CB. The Ga 1 - x Mn x As alloy has a Curie temperature lower than room temperature ( ⩽ 115 K ). However this system has the advantage that it can be easily integrated into the well known GaAs/AlAs technology. Our system is described by a tight-binding Hamiltonian. The hole–hole interaction is calculated in the Hartree approximation and the charge distribution of the system and the potential profile are calculated selfconsistently.