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The role of spatial dependence of recombination centres on the switching time in junction diodes is analysed. The switching time is dependent on the sign and value of the capture centres and charge-carrier gradients.
The recovery behaviour of p-n junctions is of great importance in computer circuit design. The switching time analysis of diodes has been carried out by Kingston (1954), Lax and Neustadter (1954), Moll et al. (1962), Kuno (1964) and other authors.
The measurement of switching time is used to determine the minority-carrier lifetime in the base material of diodes (Mielke 1971). But, in these theories, the role of spatial dependence of recombination centres was not taken into account.
Dolocan (1968, 1969) has shown that the gradual capture may lead to the improvement of the characteristics of semiconductor devices, this depending on the sign of the charge carriers and lifetime gradients. It is the purpose of this paper to give an analytic treatment of the switching time in the presence of gradual capture. [ABSTRACT FROM AUTHOR]

In this paper the gradual capture effect on the generation-recombination current in the space-charge region for an asymmetrical junction is studied. The theory is applied to the p-n InSb diodes. At forward bias, when the lifetime increases in the direction from p region to n region, the results we have obtained show that the current increases more rapidly with voltage than in the reverse case.
In this paper we shall take into account the gradual capture effect on the generation-recombination current in the space-charge region for an asymmetrical junction. [ABSTRACT FROM AUTHOR]

The influence of gradual capture on the cut-off frequency of p-n-p transistors is studied.
The results obtained show that the p-n-p transistor with narrow base in which the lifetime increases in the direction of the hole diffusion may be used at higher frequencies than the p-n-p transistor in which a reverse situation occurs.
The theory of p-n junctions and transistors was given by Shockley (1949). The p-n-p transistors with variable signals have also been considered in later publications (Zawels 1954, Giacoletto 1954, Lo et al. 1956).
Recently, Dolocan has considered the role of gradual capture in p-n junctions with variable signals (1968) and with d.c. signals (1969). It is the purpose of this paper to present an analytic treatment of p-n-p transistors with variable signals by taking into account the gradual distribution of the capture centres' concentration. [ABSTRACT FROM AUTHOR]

The p-n junction in the electric and magnetic fields is studied. The results obtained show that the magnetosensitivity of the high-level current is greater than the magnetosensitivity of the low-level current. The influence of the electric field of the neutral regions on the I-V characteristics of p-n junctions is discussed.
The theory of the p-n junctions was given by Shoekley (1949). The voltage dependence of the arbitrary-level current has also been considered in later publications (Jonscher 1958, Stafeev I959, van Vliet 1966, Barber 1969).
In p-n junctions with large basewidth it was observed that there was an increase in the magnetosensitivity of the high-level current (Melngailis and Redicker 1962, Karakushan and Stafeev 1964). The magnetosensitivity of the current depends on the ratio of basewidth to carrier diffusion length.
It is the purpose of this paper to present an analytic treatment of the p-n junction situated in electric and magnetic fields at low and high injection levels. [ABSTRACT FROM AUTHOR]

The role of gradual capture in p-n junctions and transistors at a.e. voltage was studied.
The results obtained show that the diffusion capacity of the p-n junction in the case where the carrier lifetime increases in the direction of the carrier diffusion is greater than in the reverse case. But for p-n junction resistance a reverse situation occurs. [ABSTRACT FROM AUTHOR]

The precise manipulation of transverse magnetic domain walls in finite/infinite nanowires with artificial defects under the influence of very short spin-polarized current pulses is investigated. We show that for a classical 3d ferromagnet material like nickel, the exact positioning of the domain walls at room temperature is possible only for pulses with very short rise and fall time that move the domain wall reliably to nearest neighboring pinning position. The influence of the shape of the current pulse and of the transient effects on the phase diagram current-pulse length are discussed. We show that large transient effects appear even when α=β, below a critical value, due to the domain wall distortion caused by the current pulse shape and the presence of the notches. The transient effects can oppose or amplify the spin-transfer torque (STT), depending on the ratio β/α. This enlarges the physical comprehension of the domain wall (DW) motion under STT and opens the route to the DW displacement in both directions with unipolar currents. [ABSTRACT FROM AUTHOR]

The nonlinear dynamics of a transverse domain wall (TDW) in permalloy and nickel nanostrips with two artificially patterned pinning centers is studied numerically up to rf frequencies. The phase diagram frequency-driving amplitude shows a rich variety of dynamical behaviors depending on the material parameters and the type and shape of pinning centers. We find that T-shaped traps (antinotches) create a classical double well Duffing potential that leads to a small chaotic region in the case of nickel and a large one for Py. In contrast, the rectangular constrictions (notches) create an exponential potential that leads to larger chaotic regions interspersed with periodic windows for both Py and Ni. The influence of temperature manifests itself by enlarging the chaotic region and activating thermal jumps between the pinning sites while reducing the depinning field at low frequency in the notched strips. [ABSTRACT FROM AUTHOR]

MnCoGe thin films were produced using simultaneous magnetron sputtering of Mn, Co, and Ge on SiO 2 , followed by non-diffusive reaction. The MnCoGe compound begins to form at ∼588 K, and structural characterizations show that the obtained MnCoGe film is polycrystalline with the hexagonal Ni 2 In-type structure. This structure is found to be stable from 873 K down to room temperature, the expected hexagonal/orthorhombic structural transition being prevented. The film exhibits a lower average Mn composition than the standard MnCoGe stoichiometry. Furthermore, small clusters (<3 nm) forming planar distributions parallel to the sample surface are observed. They are regularly located every ∼11 nm in the specimen depth. They mainly contain Mn and O atoms. Magnetic characterizations show very good magnetic properties, allowing the perpendicular and parallel magnetocrystalline anisotropy constants to be measured down to 100 K, using the Chappert model to fit ferromagnetic resonance measurements. The film magnetic properties match the properties of bulk stoichiometric MnCoGe in the hexagonal structure, with a Curie temperature of ∼269 K and a negligible coercive field at room temperature. The only difference between the magnetic properties of bulk and thin film specimens appears to be the film shape anisotropy, forcing the internal magnetic field to be contained in the film plane. [ABSTRACT FROM AUTHOR]

We present direct imaging of magnetic flux structures over the ab face of the anisotropic, spin-triplet superconductor Sr2RuO4 using a scanning microSQUID force microscope. Individual vortices with a single flux quantum were observed at low magnetic fields applied along the out-of-pane direction. At intermediate fields, the direct imaging revealed coalescing of vortices and the formation of flux domains. Our observations imply the existence of a mechanism in this material for bringing vortices together overcoming the conventional repulsive vortex-vortex interaction.