Spin dependent device transport, where the distinction between spin up and spin
down carriers arises from the presence of local diluted magnetic semiconductor (DMS)
regions, offers the possibility of magnetic field control of transport. This paper describes
through the use of numerical solutions to the spin dependent Wigner distribution function, the
means by which dilute magnetic semiconductors layers can lead to a magnetic field dependent
break in the symmetry of superlattice structures. Specific examples area given in which
all of the barriers are composed of DMS layers, and as a function of magnetic field there is an
alteration in the relative population of spin up and spin down carriers. The symmetry breaking
structure consists of a superlattice with a single DMS layer. As a function of magnetic
field the barrier is higher for one spin state and lower of the other leading to a local region of
charge accumulation that is not present in periodic lattice. The application of this broken
symmetry to the creation of nucleation sites for high field domains, and in some cases alter
the properties of the propagating domain is discussed.
The 2DEG adjacent to a diluted magnetic semiconductor heterobarrier is altered in the presence of a magnetic field. The alteration is dependent upon at least three factors: the Zeeman energy, the self consistent potential energy and the equilibrium distribution. Concentrating on the first two features we present results for the alteration of the 2DEG for a spin heterodiode configuration and for a single barrier DMS structure, demonstrating that the 2DEG can be modified by a magnetic field, thereby permitting the magnetic field to function as a gate in two terminal structures with spin dependent contacts.
We present the development of a set of electron and hole quantum transport equations for barrier devices with dilute magnetic semiconductor (DMS) regions. The equations are developed from the time dependent equation of motion of the density matrix equation in the coordinate representation, leading to both the transient spin Wigner equations and the 'classical' spin drift and diffusion equations for high 'g' factor DMS materials. The role of DMS layers is illustrated for two structures; one where the DMS layer is confined to the first barrier, and another with DMS emitter and collector barriers. In each case we obtain the spinup and spindown carrier and current distributions, from self-consistent solutions to the transient spin dependent Wigner equation. Negative differential conductance as well as the significant unequal spinup and spin down charge distributions are obtained.
The spin dependent Wigner function is implemented to obtain the IV characteristics of a double barrier resonant tunneling diode with DMS layers. The structure distinguishes between spin-up and spin-down carriers, each of which experiences resonance at different magnetic field dependent bias levels. The results demonstrate the magnetic field dependence of the IV characteristics and illustrate the magnetic field dependence of relative spin-up and spin-down carriers.
The transient behavior of semiconductor devices within the framework of density operators, the density matrix and the quantum hydrodynamic moment equations are reviewed. A capacitive-inductive transition, near 4 THz for two terminal double barrier structures within the framework of the quantum hydrodynamic equations is discussed.
In this paper, it is demonstrated that establishing metal-semiconductor interfaces at the heterojunctions of polar semiconductor quantum wells introduces a set of boundary conditions that dramatically reduces or eliminates unwanted carrier energy loss caused by interactions with interface longitudinal-optical (LO) phonon modes.