Electrical Transport Properties of Annealed Undoped InP

The electrical properties of annealed undoped n-type InP are studied by temperature dependent Hall effect (TDH) and current-voltage (I-V) measurements for semiconducting and semi-insulating samples, receptively. Defect band conduction in annealed semiconducting InP can be observed from TDH measurement, which is similar to those of as-grown unintentionally doped InP with low carrier concentration and moderate compensation. The I-V curves of annealed undoped SI InP exhibit ohmic property in the applied field region up to the onset of breakdown. Such a result is different from that of as-grown Fe-doped SI InP which has a nonlinear region in I-V curve explained by the theory of space charge limited current.

Transport properties in a gated heterostructure with a trapezoidal AlxGa1-xAs barrier layer

By replacing the flat (Ga1-xAlx)As barrier layer with a trapezoidal AlxGa1-xAs barrier layer, a conventional heterostructure can be operated in enhancement mode. The sheet density of two-dimensional electron gas (2DEG) in the structure can be tuned linearly from N-2D = 0.3 x 10(11) cm(-2) to N-2D = 4.3 x 10(11) cm(-2) by changing the bias on the top gate. The present scheme for gated heterostructures is easy to fabricate and does not require the use of self-alignment photolithography or the deposition of insulating layers. In addition, this scheme facilitates the initial electrical contact to 2DEG. Although, the highest electron mobility obtained for the moment is limited by the background doping level of heterostructures, the mobility should be improved substantially in the future. (C) 2009 Elsevier B.V. All rights reserved.

Electron transport properties of MM-HEMT with varied channel indium contents

Transport properties of two-dimensional electron gas (2DEG) are crucial to metamorphic high-electron-mobility transistors (MM-HEMT). We have investigated the variations of subband electron mobility and concentration versus temperature from Shubnikov-de Hass oscillations., and variable temperature Hall measurements. The results indicate that the electrical performance is the best when the In content is 0.65 in the channel for MM-HEMT. When the In content exceeds 0.65, a large lattice mismatch will cause dislocations and result in the decrease of mobility and the fall of performance in materials and devices.

Preparation and transport properties of a bulk icosahedral quasicrystalline Ti45Zr35Ni17Cu3 alloy

A bulk alloy which consists of the single icosahedral quasicrystalline phase (I-phase) in Ti45Zr35Ni17CU3 alloy has been fabricated by mechanical alloying and subsequent pulse discharge sintering technique. Crystallographic structure analyses show that the bulk alloy is an I-phase. The transport properties of the bulk alloy are examined, and the results show that the room-temperature thermal conductivity is 5.347 W K-(1) m(-1), and the electrical conductivity decreases with increasing the temperature from 300 to 450K. The Seebeck coefficient is negative at the temperature range from 300 to 360K, and changes to positive from 370 to 450K. Hall effect measurements indicate the bulk I-phase alloy has a high carrier concentration. The specific heat capacity increases when the temperature increases from 280 to 324 K.

Transport Properties And Induced Voltage In The Structure Of Water-Filled Single-Walled Boron-Nitrogen Nanotubes

Density functional theory/molecular dynamics simulations were employed to give insights into the mechanism of voltage generation based on a water-filled single-walled boron-nitrogen nanotube (SWBNNT). Our calculations showed that (1) the transport properties of confined water in a SWBNNT are different from those of bulk water in view of configuration, the diffusion coefficient, the dipole orientation, and the density distribution, and (2) a voltage difference of several millivolts would generate between the two ends of a SWBNNT due to interactions between the water dipole chains and charge carriers in the tube. Therefore, this structure of a water-filled SWBNNT can be a promising candidate for a synthetic nanoscale power cell as well as a practical nanopower harvesting device.

Transport properties and induced voltage in the structure of water-filled single-walled boron-nitrogen nanotubes

Density functional theory/molecular dynamics simulations were employed to give insights into the mechanism of voltage generation based on a water-filled single-walled boron-nitrogen nanotube (SWBNNT). Our calculations showed that (1) the transport properties of confined water in a SWBNNT are different from those of bulk water in view of configuration the diffusion coefficient the dipole orientation and the density distribution and (2) a voltage difference of several millivolts would generate between the two ends of a SWBNNT due to interactions between the water dipole chains and charge carriers in the tube. Therefore this structure of a water-filled SWBNNT can be a promising candidate for a synthetic nanoscale power cell as well as a practical nanopower harvesting device.

Electrical transport in metallic films

On the basis of the Boltzmann equation, the authors propose a model that includes scattering from both film surfaces and grain boundaries, and have studied the quasiclassical electrical transport in metallic films. The in-plane electric conductivity of metallic films is obtained, and the theoretical results are shown to be in good agreement with experimental data. We also give the relation between temperature coefficient of resistivity and thickness of metallic films and make a comparison with experiment. <(C)> 2004 American Institute of Physics.

Electron transport properties of In0.53Ga0.47As/In0.52Al0.48As quantum wells with two occupied subbands

Magnetotransport properties of two-dimensional electron gas have been investigated for three In0.53Ga0.47As/In0.52Al0.48As quantum well samples having two occupied subbands with different well widths. When the intersubband scattering is considered, we have obtained the subband density, transport scattering time, quantum scattering time and intersubband scattering time, respectively, by analyzing the result of fast Fourier transform of the first derivative of Shubnikov-de Haas oscillations. It is found that the main scattering mechanism is due to small-angle scattering, such as ionized impurity scattering, for the first subband electrons.

Fabrication and transport properties of ZnO/Nb-1 wt %-doped SrTiO3 epitaxial heterojunctions

(110) ZnO/(001) Nb-1 wt %-doped SrTiO3 n-n type heteroepitaxial junctions were fabricated using the pulse laser deposition method. A diodelike current behavior was observed. Different from conventional p-n junctions or Schottky diodes, the diffusion voltage was found to increase with temperature. At all temperatures, the forward current was perfectly fitted on the thermionic emission model. The band bending at the interface can qualitatively explain our results, and the extracted high ideality factor at low temperatures, as well as large saturation currents, is ascribed to the deep-level-assisted tunneling current through the junction. (C) 2008 American Institute of Physics.

Influences of As flux on the lattice constants, magnetic and transport properties of (Ga, Mn)As epilayers

A series of (Ga, Mn)As epilayers have been prepared on semi-insulating GaAs (001) substrates at 230 degrees C by molecular-beam epitaxy under fixed temperatures of Ga and Mn cells and varied temperatures of the As cell. By systematically studying the lattice constants, magnetic and magneto-transport properties in a self-consistent manner, we find that the concentration of As antisites monotonically increases with increasing As flux, while the concentration of interstitial Mn defects decreases with it. Such a trend sensitively affects the properties of (Ga, Mn)As epilayers. (c) 2006 Elsevier Ltd. All rights reserved.

Transport properties through quantum dot in a vertical electric field

The transport properties through a quantum dot are calculated using the recursion method. The results show that the electric fields can move the conductive peaks along the high- and low-energies. The electric field changes the intensity of conductance slightly. Our theoretical results should be useful for researching and making low-dimensional semiconductor optoelectronic devices. (C) 2002 Elsevier Science B.V. All rights reserved.

Influence of transverse interdot coupling on transport properties of an Aharonov-Bohm structure composed by two dots and two reservoirs

We derive the modified rate equations for an Aharonov-Bohm (AB) ring with two transversely coupled quantum dots (QD's) embedded in two arms in the presence of a magnetic field. We find that the interdot coupling between the two QD's can cause a temporal oscillation in electron occupation at the initial stage of the quantum dynamics, while the source-drain current decays monotonically to a stationary value. On the other hand, the interdot coupling equivalently divides the AB ring into two coupled subrings. That also destroys the normal AB oscillations with a period of 2pi, and generates new and complex periodic oscillations with their periods varying in a linear manner as the ratio between two magnetic fluxes (each penetrates one AB subring) increases. Furthermore, the interference between two subrings is also evident from the observation of the perturbed fundamental AB oscillation.

Electronic structure and transport properties of quantum rings in a magnetic field

The electronic structure of quantum rings is studied in the framework of the effective-mass theory and the two dimensional hard wall approximation. In cases of both the absence and presence of a magnetic field the electron momenta of confined states and the Coulomb energies of two electrons are given as functions of the angular momentum, inner radius, and magnetic-field strength. By comparing with experiments it is found that the width of the real confinement potential is 14 nm, much smaller than the phenomenal width. The Coulomb energy of two electrons is calculated as 11.1 meV. The quantum waveguide transport properties of Aharonov-Bohm (AB) rings are studied complementarily, and it is found that the correspondence of the positions of resonant peaks in AB rings and the momentum of confined states in closed rings is good for thin rings, representing a type of resonant tunneling.

Electrical transport through individual DNA molecules

A theoretical model is presented to describe electrical transport through individual DNA molecules. By contacting the proposed model with the experimentally measured data, a variety of valuable quantities are identified. The partially decoherent nature on the guanine-cytosine (GC) pairs of DNA is also elaborated in contrast to the completely incoherent hopping mechanism discussed in the context of charge transfer experiments. (C) 2001 American Institute of Physics.

Carrier transport properties of the (n)nc-Si : H/(p)c-Si heterojunction

Phosphor-doped nano-crystalline silicon ((n))nc-Si:H) films are successfully grown on the p-type (100) oriented crystal silicon ((p) c-Si) substrate by conventional plasma-enhanced chemical vapor deposition method. The films are obtained using high H-2 diluted SiH4 as a reaction gas source and using PH3 as the doping gas source of phosphor atoms. Futhermore, the heterojunction diodes are also fabricated by using (n)nc-Si:H films and (p)c-Si substrate. I-V properties are investigated in the temperature range of 230-420K. The experimental results domenstrate that (n)nc-Si:H/(p) c-Si heterojunction is a typical abrupt heterojunction having good rectifing and temperature properties. Carrier transport mechanisms are tunneling - recombination model at forward bias voltages. In the range of low bias voltages ( V-F< 0.8 V), the current is determined by recombination at the (n)nc-Si:H side of the space charge region, while the current becomes tunneing at higher bias voltages( V-F>1.0 V). The present heterojunction has high reverse breakdown voltage ( > - 75 V) and low reverse current (approximate to nA).