V. A. Guzenko

Weak antilocalization in a polarization-doped AlxGa1−xN∕GaN heterostructure with single subband occupation

Spin-orbit scattering in a polarization-doped Al0.30Ga0.70N∕GaN two-dimensional electron gas with one occupied subband is studied at low temperatures. At low magnetic fields weak antilocalization is observed, which proves that spin-orbit scattering occurs in the two-dimensional electron gas. From measurements at various temperatures the elastic scattering time τtr, the dephasing time τϕ, and the spin-orbit scattering time τso are extracted. Measurements in tilted magnetic fields were performed, in order to separate spin and orbital effects.

Zeeman splitting in ballistic GaInAs∕InP split-gate quantum point contacts

The Zeeman splitting in ballistic GaxIn1−xAs∕InP split-gate point contacts was investigated. The measurements were performed in a magnetic field perpendicular to the plane of the two-dimensional electron gas. The Zeeman energy splitting between the one-dimensional subbands was determined by measuring the differential conductance as a function of the dc source-drain voltage across the point contact. The g factor of approximately 4.0 extracted from measurements at various magnetic fields agrees well to the value obtained by other methods for this type of heterostructure.

Magnetic and structural properties of GaN thin layers implanted with Mn, Cr, or V ions

We report on magnetic and structural properties of n- and p-type GaN layers implanted with Mn, Cr, and V. The samples were subsequently annealed in a N2 atmosphere at a constant temperature in the range between 700 and 1050°C. Measurements of the magnetization as a function of magnetic field as well as of the temperature show typical paramagnetic behavior. In addition, a weak antiferromagnetic coupling between the implanted ions was observed. 3d-metal rich precipitates of crystalline nature are revealed by high resolution transmission electron microscopy.

Rashba effect in InGaAs∕InP parallel quantum wires

We report on the Rashba effect in InGaAs∕InP quantum wires with an effective width ranging from 1.18μm down to 210nm. By measuring 160 wires in parallel universal conductance, fluctuations could be suppressed so that the characteristic beating effect in the magnetorestistance was observable down to very low magnetic fields. A characteristic shift of the nodes in the beating pattern was found for decreasing wire width. By assuming a realistic soft-wall potential, the experimentally observed node positions could be reproduced. For the range of measured wires, our study confirms that the Rashba coupling parameter does not change with wire width.

Spin–orbit coupling in GaxIn1−xAs/InP two-dimensional electron gases and quantum wire structures

In this work, the effect of spin–orbit coupling in two-dimensional electron gases and quantum wire structures is discussed. First, the theoretical framework is introduced including spin–orbit coupling due to structural inversion asymmetry, the so-called Rashba effect, as well as the Dresselhaus term. The latter originates from bulk inversion asymmetry. With regard to wire structures, special attention is devoted to the influence of the particular shape of the confinement potential on the energy spectrum. As a model system GaxIn1−xAs/InP heterostructures are chosen, where different thicknesses of the strained Ga0.23In0.77As channel layer were introduced, in order to adjust the strength of the spin–orbit coupling. Hall bar structures as well as sets of identical wires with different widths were prepared. In two-dimensional electron gases, the strength of the spin–orbit coupling was extracted by analyzing the characteristic beating pattern in the Shubnikov–de Haas oscillations. In addition, the weak antilocalization was utilized to obtain information on the spin–orbit coupling. It is shown that for decreasing width of the strained layer the Rashba effect, which dominates in our layer systems, is increased. This behavior is attributed to the larger interface contribution if the electron wavefunction is strongly confined. The measurements on the wire structures revealed a transition from weak antilocalization to weak localization if the wire width is decreased. This effect is attributed to an enhanced spin diffusion length for strongly confined systems.

Shot noise of large charge quanta in superconductor/semiconductor/superconductor junctions

We have found experimentally that the noise of ballistic electron transport in a superconductor/semiconductor/superconductor junction is enhanced relative to the value given by the general relation,

Spin‐splitting characterization of an InGaSb 2DEG by using magnetoresistance measurements with tilted magnetic fields

{S}_{V}=2eI{R}^{2}\phantom{\rule{0.2em}{0ex}}\mathrm{coth}(eV∕2kT)

Supercurrent control in a multi-terminal Nb-InGaAs/InP junction with Nb injector electrodes

, for two voltage regions in which this expression reduces to its thermal and shot noise limits. The noise enhancement is explained by the presence of large charge quanta, with an effective charge

Suppression of weak antilocalization in Ga x In 1 − x As ∕ InP narrow quantum wires

q*=(1+2\ensuremath{\Delta}∕eV)e

Effect of Rashba spin-orbit coupling on magnetotransport in InGaAs/InP quantum wire structures

, that generate a noise spectrum