Abstract
Nonlinear transport through diluted magnetic semiconductor nanostructures is investigated. We have considered a II–VI multiquantum well nanostructure whose wells are selectively doped with Mn. The response to a dc voltage bias may be either a stationary or an oscillatory current. We have studied the transition from stationary to time-dependent current as a function of the doping density and the number of quantum wells. Analysis and numerical solution of a nonlinear spin transport model shows that the current in a structure without magnetic impurities is stationary, whereas current oscillations may appear if at least one well contains magnetic impurities. For long structures having two wells with magnetic impurities, a detailed analysis of nucleation of charge dipole domains shows that self-sustained current oscillations are caused by repeated triggering of dipole domains at the magnetic wells and motion towards the collector. Depending on the location of the magnetic wells and the voltage, dipole domains may be triggered at both wells or at only one. In the latter case, the well closer to the collector may inhibit domain motion between the first and the second well inside the structure. Our study could allow design of oscillatory spin-polarized current injectors.
Highlights
Nonlinear transport through diluted magnetic semiconductor nanostructures is investigated
We analyze nonlinear electron spin dynamics in an n-doped dc voltage biased semiconductor multiquantum well structure (MQWS) having one or more of its wells doped with magnetic impurities (Mn)
We have studied the phase diagram, current–voltage characteristics and sustained current oscillations (SSCOs) for a MQWS with one or two QWs doped with magnetic impurities
Summary
The sample under consideration consists of an n-doped ZnSe/(Zn,Cd,Mn)Se weakly coupled. 5 2 and the exchange interaction between the Mn local moments and the conduction band electrons is ferromagnetic in II–VI QWs. Using the virtual crystal and mean field approximations, the effect of the exchange interaction is to make the sub-band energies spin dependent in those. Ni+, ni− and −Fi are the two-dimensional (2D) spin-up and spin-down electron densities, and the average electric field at the ith SL period (which starts at the right end of the (i − 1)th barrier and finishes at the right end of the ith barrier), respectively. ND, ε, −e, l = d + w, and −Ji±→i+1 are the 2D doping density at the QWs, the average permittivity, the electron charge, the width of a SL period (d and w are barrier and well widths) and the tunneling current density across the ith barrier, respectively.
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