Methods for spin injection managing in inGaAs/GaAs/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/CoPt spin light-emitting diodes

Spin injection in CoPt/Al₂O₃/(Al)GaAs spin light-emitting diodes (SLEDs) was studied. The oscillations of the degree of circular polarization upon variation of a distance between the active region of the SLED and a CoPt ferromagnetic injector were observed. The oscillations depend neither on a SLED material (GaAs or AlGaAs), nor on the type of injected spin-polarized carriers (electrons and holes) and are related to the action of a perpendicular magnetic field on the injected spin-polarized carriers that causes their precession. During the transfer to the active region through a distance of 50–100 nm from the injector, a z–component of a spin changes a phase that is detected experimentally as the change in sign of the degree of circular polarization of luminescence. Conceivably, a source of the internal magnetic field leading to spin precession is the magnetic field of the nonuniformly magnetized CoPt contact.     

Heterostructures with InGaAs/GaAs quantum dots doped with transition elements: II. Study of the circularly polarized luminescence

Optical and transport properties of the heterostructure with the InAs/GaAs quantum dots doped with manganese or chromium atoms in the course of growth using metal-organic vapor phase epitaxy (MOVPE) are analyzed. Circularly polarized luminescence was obtained due to doping of quantum dots with the Mn or Cr atoms. The sign of the degree of circular polarization was found to depend on the dopant. The effect is interpreted using specific features of the radiative recombination in quantum dots in the presence of resident electrons and holes.     

Electromagnetic radiation from filamentary sources in the presence of axially magnetized cylindrical plasma scatterers

Electromagnetic radiation from filamentary electric-dipole and magnetic-current sources of infinite length in the presence of gyrotropic cylindrical scatterers in the surrounding free space is studied. The scatterers are assumed to be infinitely long, axially magnetized circular plasma columns parallel to the axis of the filamentary source. The field and the radiation pattern of each source are calculated in the case where the source frequency is equal to one of the surface plasmon resonance frequencies of the cylindrical scatterers. It is shown that the presence of even a single resonant magnetized plasma scatterer of small electrical radius or a few such scatterers significantly affects the total fields of the filamentary sources, so that their radiation patterns become essentially different from those in the absence of scatterers or the presence of isotropic scatterers of the same shape and size. It is concluded that the radiation characteristics of the considered sources can efficiently be controlled using their resonance interaction with the neighboring gyrotropic scatterers.     

Beatings of Shubnikov-de Haas oscillations in a two-dimensional hole system in an InGaAs quantum well

The magnetoresistance of an InGaAs/GaAs heterostructure with a two-dimensional hole channel has been measured in quantizing magnetic fields. Beatings of Shubnikov-de Haas oscillations have been observed, which indicate that the spin degeneracy of the system is lifted owing to the spin-orbit interaction. The oscillation pattern is independent of the magnetic field component parallel to the two-dimensional system; this independence is characteristic of size-quantization heavy-hole subbands.     

Effect of compressive and tensile stresses in GaMnAs layers on their magnetic properties

The effect of elastic stresses (compressive, tensile) on the magnetic properties of epitaxial GaMnAs layers prepared by laser deposition of solid-state targets in a gas atmosphere on different buffer sublayers (In _x Ga_{1 − x} As and In _x Ga_{1 − x} P) and substrates (GaAs, InP) has been investigated. It has been established from the investigations of magnetic-field dependences of the Hall resistance that all layers exhibit ferromagnetic properties with the Curie temperature ∼50 K. It has been shown that, in the case of tensile stresses in GaMnAs layers (In _x Ga_{1 − x} As and In _x Ga_{1 − x} P buffers and InP substrate), the anomalous Hall effect shape demonstrates a predominant orientation of the easy-magnetization axis in the growth direction, unlike the GaMnAs layers prepared on a GaAs substrate (with compressive stresses), which demonstrate the predominance of the component of the magnetization vector in the layer plane.     

Formation of MnAs and MnP layers by reactive laser sputtering

We show that the technique of pulsed laser sputtering of metallic manganese in a flow of hydrides (arsine or phosphine) allows the deposition of half-metallic MnB ⁵ compound layers on GaAs (100) substrates. The crystal structure, magneto-optical, and galvanomagnetic properties of the layers are determined by synthesis conditions, mainly by substrate temperature. It is established that the MnAs and MnP layers are ferromagnetic at temperatures up to 300 K.     

Plasma-Chemical Synthesis of Lead Sulphide Thin Films for Near-IR Photodetectors

Plasma Chemistry and Plasma Processing - Lead sulfide (PbS) thin films of different morphology were synthesized via direct interaction of lead and sulfur vapors. Low temperature nonequilibrium RF...     

Whistler Wave Emission from a Modulated Electron Beam in a Collisional Magnetoplasma in the Presence of a Density Duct

We study the radiation from a modulated electron beam injected along the axis of a cylindrical density duct in a magnetoplasma. An expression for the average power lost by the beam at the modulation frequency is obtained and analyzed. It is shown that in the case of Cerenkov resonance of the beam with a weakly damped whistler mode of an enhanced-density duct, a noticeable increase in this power is possible compared with the case where the beam is injected in a homogeneous background magnetoplasma. Based on the results of numerical calculations performed for conditions of the Earth's ionosphere, we give estimates of an increase in the power radiated from the beam in the whistler frequency range in the presence of a cylindrical duct with enhanced density. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 730–742, September 2005.     

Phase Separation in GaMnAs Layers Grown by Laser Pulsed Deposition

GaMnAs layers grown by pulsed laser deposition were studied by magneto-optical transversal Kerr effect spectroscopy, spectral ellipsometry, resistivity and the Hall effect measurements, and magnetometry. The growth regimes for magnetically inhomogeneous layers containing Mn-enriched ferromagnetic regions with different composition and sizes were established. The layers grown at a temperature of 300°C exhibit a ferromagnetic behavior at temperatures below 80 K, which is conditioned by the presence of local ferromagnetic (Ga,Mn)As regions in the paramagnetic matrix. The nature of peculiarities in the TKE spectrum of these layers is discussed.     

Whistler channeling in ducts with enhanced density in a magnetoactive plasma

We study the guided propagation of whistler waves along the density ducts created in a magnetoactive plasma under thermal nonlinear conditions. It is found that the thermal diffusion-driven redistribution of plasma due to electron heating in the quasistatic field of a current loop of fairly large radius leads to the formation of a duct with enhanced density. Based on experimental data and theoretical calculations, it is shown that such a duct can sustain the weakly decaying whistler modes excited by a magnetic-type antenna immersed in it. Radiophysical Research Institute, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 384–394, March, 1998.