Narrow Results

This paper presents of development of quantum transport equations for barrier devices with both electron and hole transport in dilute magnetic semiconductor (DMS) structures. The equations are developed from the time dependent equation of motion of the density matrix equation in the coordinate representation, from which both the spin drift and diffusion and transient Wigner equations are obtained, for a system in which high 'g' factor materials result in significant spin-splitting of the valence and conduction bands. Then for a structure in which the DMS layer is confined to the first barrier solutions to the coupled Poisson's and spin dependent Wigner equations yield the IV and carrier distributions. Negative differential conductance as well as the significant unequal spinup and spin down charge distributions are obtained.

We review the results of our current research on quantum engineering which include the theory, modeling and simulations of quantum devices for potential applications to threat reduction and homeland security. In particular, we discuss: (i) scalable solid-state quantum computation with qubits based on (a) nuclear spins of impurity atoms in solids, (b) superconducting junctions, and (c) unpaired electron spins of spin radicals in self-assembled organic materials; (ii) quantum neural devices; (iii) quantum annealing; (iv) novel magnetic memory devices based on magnetic tunneling junctions with large tunneling magnetoresistance; (v) terahertz detectors based on microcantilever as a light pressure sensor; (vi) BEC based interferometers; (vii) quantum microscopes with a single-spin resolution based on (a) a magnetic resonant force microscopy and (b) an optically detected magnetic resonance; and (viii) novel approach for suppression of fluctuations in free space high-speed optical communication. Finally, we describe the similarities between the behavior of cross sections in reactions with heavy nuclei in the regions of strongly overlapped resonances and electron conductivity in semiconductor heterostructures.

Two terminal devices have traditionally provided band-structure based high frequency operation. Third terminal control often involves hybrid design approaches. The presence of diluted magnetic semiconductor layers in device fabrication should permit the magnetic field to function as a pseudo-third terminal. This is discussed for single barrier, double barrier and superlattice structures, where control is demonstrated. The limits of high frequency operation are discussed in general terms with application to barrier devices and superlattices containing DMS layers.

Recent advances in successful operation of silicon-based devices where transport is dependent on electron magnetic moment, or “spin”, could provide a future alternative to CMOS for logic processing. The basics of this spin electronics (Spintronics) technology are discussed and the specific methods necessary for application to silicon are described. Fundamental measurements of spin polarization and spin precession are demonstrated.