Ferromagnetism in Mn-doped GaAs layers: Effects of laser annealing

The properties of Mn-doped GaAs layers grown by laser deposition were investigated with measurements of Hall effect and magneto-optical Kerr effect (MOKE). The electrical and magnetic parameters of the layers were defined by growth temperature and quantity of sputtered Mn. It was shown that room-temperature ferromagnetism is revealed by MOKE and, after ruby laser 25 ns pulse annealing, by Hall effect measurements.     

Properties of MnSb/GaAs heterostructures

MnSb layers are deposited on GaAs(100) via the laser ablation of Mn and Sb targets. The magnetic field dependences of the transverse Kerr effect display magnetic anisotropy and magnetization jumps. Measurements of the Hall effect reveal a hysteresis loop at temperatures of up to 300 K.     

Properties of CoPt ferromagnetic layers for application in spin light-emitting diodes

The magnetic properties of Co₄₅Pt₅₅ films deposited by electron-beam evaporation in vacuum have been studied. The measurements of the Faraday and Kerr magnetooptical effects confirm the presence of the easy-magnetization axis perpendicular to the Co₄₅Pt₅₅ surface. It is shown that the perpendicular magnetic anisotropy and the residual magnetization are retained at 300 K for a long time. The magnetic characteristics of the Co₄₅Pt₅₅ layer surface have been studied by magnetic force microscopy, and “circular” mobile magnetic structures have been detected. The spin light-emitting diodes based on In(Ga)As/GaAs heteronanostructures with Co₄₅Pt₅₅ contact layers were fabricated. These diodes emit circularly-polarized light in the absence of an external magnetic field.     

Formation of the single-phase ferromagnetic semiconductor (Ga,Mn)As by pulsed laser annealing

It is shown that (Ga,Mn)As layers formed by Mn⁺ ion implantation into GaAs and subsequent annealing by an excimer laser pulse with an energy density to 200–300 mJ/cm² feature the properties of the p-type semiconductor and ferromagnetic properties. The threshold dose of implanted ions (~10¹⁵ cm^–2) for activating Mn acceptors is determined. The sheet hole concentration and the Curie temperature increase with further increasing Mn⁺ ion dose. Hysteresis loops in the magnetic field dependences of the Hall effect, the negative magnetoresistance, and magnetic and structural studies suggest that the layers are analogues of single-phase ferromagnetic compounds (Ga,Mn)As formed by low-temperature molecular beam epitaxy.     

Photoconductive detector of circularly polarized radiation based on a MIS structure with a CoPt layer

Physics of the Solid State - A photoconductive detector of circularly polarized radiation based on the metal–insulator–semiconductor structure of CoPt/(Al2O3/SiO2/Al2O3)/InGaAs/GaAs is...     

Anomalous hall effect in Mn δ-doped GaAs/In0.17Ga0.83As/GaAs quantum wells with high hole mobility

Magnetic and magnetotransport properties of GaAs(δ〈Mn〉)/In_0.17Ga_0.83As/GaAs quantum wells with different Mn concentrations are studied. The delta-doped manganese layer has been separated from the GaAs quantum well with a spacer with an optimal thickness (3 nm), which has provided a sufficiently high hole mobility (≥10³ cm²V^?1 s^?1) in the quantum wells and their effective exchange with Mn atoms. It is found that the anomalous Hall effect (AHE) is exhibited only in a restricted temperature range above and below the Curie temperature, while the AHE is not observed in quantum wells with quasi-metallic conductivity. Thus, it is shown that the use of the AHE is inefficient in studying magnetic ordering in semiconductor systems with high-mobility carriers. The features observed in the behavior of the resistance, magnetoresistance, and Hall effect are discussed in terms of the interaction of holes with magnetic Mn ions with regard to fluctuations of their potential, hole transport on the percolation level, and hopping conduction.     

Ferromagnetism in InMnAs layers at room temperature

The InMnAs layers with ferromagnetic properties at room temperature are prepared by laser ablation. This is confirmed by the results of investigating the anomalous Hall and magneto-optical Kerr effects and by magnetic-force microscopy. According to x-ray diffraction data, the InMnAs layers have a fairly high crystal quality but contain inclusions of the MnAs hexagonal phase. An analysis of the electrical properties of the InMnAs layers suggests that the ferromagnetism revealed at room temperature cannot be accounted for by the presence of the MnAs phase but is associated with the charge carrier transfer in the InMnAs matrix.     

Influence of cluster formation on localization of optical phonons in two-dimensional pseudobinary substitutional solid solutions

The influence of the composition and short-range order of the cluster formation type on optical phonon localization in two-dimensional pseudobinary substitutional solid solutions is studied. Direct numerical calculations of the so-called inverse participation ration (IPR) are carried out, and the scaling of this parameter is studied for the fundamental modes of the spectral density of states at the Brillouin zone center of the averaged crystal. It is shown that cluster formation promotes phonon delocalization, although the nature of this effect is different for resonant and local (in the low-concentration limit) modes. The influence of the ionicity of a solid solution on localization is considered. It is shown that the Coulomb interaction neutralizes the effect of cluster formation while simultaneously decreasing the observed IPR. Based on the form of the distribution of local site absorption of an external electromagnetic field, a new physical criterion is suggested, which allows one to analyze the localization degree of phonon modes in ionic alloys.     

Formation of half-metallic MnAs and MnP layers

Half-metallic MnAs and MnP layers were grown on GaAs substrates by the laser sputtering of a metal Mn target in a hydrogen and arsine (phosphine) flow. The effect of the arsine concentration in the gascarrier and the substrate temperature (T _g = 300—450°C) on the crystal structure and electrical and magnetic properties were determined. It was shown that MnP samples grown at T _g ≥ 400°C exhibit ferromagnetic properties up to 300 K, according to Hall effect measurements.