Search results for "Semi"
showing 10 items of 3894 documents
Specific features of the electronic structure of III–VI layered semiconductors: recent results on structural and optical measurements under pressure …
2003
In this paper we review some recent results on the electronic structure of III-VI layered semiconductors and its dependence under pressure, stressing the specific features that differentiate their behaviour from that of tetrahedrally coordinated semiconductors. We will focus on several unexpected results that have led to changes in the image that was currently accepted a few years ago. Intralayer bond angles change under pressure and the layer thickness remains virtually constant or increases. As a consequence, models based in intra- and inter-layer deformation potentials fail in explaining the low pressure nonlinearity of the band gap. Numerical-atomic-orbital/density-functional-theory ele…
Effects of Nid-levels on the electronic band structure of NixCd1-xO semiconducting alloys
2017
NixCd1-xO has a ∼3 eV band edge offset and bandgap varying from 2.2 to 3.6 eV, which is potentially important for transparent electronic and photovoltaic applications. We present a systematic study of the electronic band structure of NixCd1-xO alloys across the composition range. Ion irradiation of alloy samples leads to a saturation of the electron concentration associated with pinning of the Fermi level (EF) at the Fermi stabilization energy, the common energy reference located at 4.9 eV below the vacuum level. The composition dependence of the pinned EF allows determination of the conduction band minimum (CBM) energy relative to the vacuum level. The unusually strong deviation of the CBM…
Effect of Pressure on Direct Optical Transitions of ?-InSe
2000
We have investigated the effect of hydrostatic pressure on direct optical transitions of the layered semiconductor γ-InSe by photoreflectance (PR) spectroscopy (T = 300 K). In addition, electroreflectance (ER) measurements were performed at ambient pressure. Six structures are resolved in the ER spectra in the energy range from 1.1 to 3.6 eV. The pressure dependence of four of these structures was determined by PR spectroscopy for pressures up to 8 GPa. In order to assign the features observed above the fundamental gap we have carried out band structure calculations for InSe at ambient pressure using a full-potential linear augmented plane wave method. Based on calculated band gap deformati…
X-ray-absorption fine-structure study of ZnSexTe1−x alloys
2004
X-ray-absorption fine-structure experiments at different temperatures in ZnSexTe1−x (x=0, 0.1, 0.2, 0.55, 0.81, 0.93, 0.99, and 1.0) have been performed in order to obtain information about the structural relaxation and disorder effects occurring in the alloys. First and second neighbor distance distributions have been characterized at the Se and Zn K edges, using multiple-edge and multiple-scattering data analysis. The first neighbor distance distribution was found to be bimodal. The static disorder associated with the Zn–Te distance variance did not depend appreciably on composition. On the other hand, the static disorder associated with the Zn–Se distance increased as the Se content dimi…
Magnetic and Electronic Properties ofRENiBi (RE = Pr, Sm, Gd-Tm, Lu) Compounds
2008
Resistivity and magnetic measurements were used to examine the ternary rare earth compounds RENiBi (RE = Pr, Sm, Gd-Tm, Lu). These compounds order antiferromagnetically with TN below 16 K (RE = Pr, Sm, Gd-Tm) or are paramagnetic (LuNiBi). For some of these compounds a metal–insulator transition was found. The metal–insulator transition temperature depends strongly on the preparation conditions. Both the magnetic ground states and the resistance behavior are in good agreement with electronic band structure calculations.
Thickness scaling of space-charge-limited currents in organic layers with field- or density-dependent mobility
2006
An exact solution is provided for the current density-voltage (J –V) characteristics of space-charge limited transport of a single carrier in organic layers with field-dependent mobility of the type μ (E) = μ0 exp (γ √E. The general scaling relationship for field-dependent mobility occurs in terms of the variables JL and V /L. For the density-dependence of the mobility found in organic field-effect transistor measurements, the thickness scaling occurs in terms of different variables, J1/βL and V /L. The proposed scaling is a useful test for distinguishing field- and carrier density-dependent mobility in disordered organic semiconductors. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Phonon Scattering through a Local Anisotropic Structural Disorder in the Thermoelectric Solid Solution Cu_2Zn_(1−x)Fe_xGeSe_4
2013
Inspired by the promising thermoelectric properties of chalcopyrite-like quaternary chalcogenides, here we describe the synthesis and characterization of the solid solution Cu(2)Zn(1-x)Fe(x)GeSe(4). Upon substitution of Zn with the isoelectronic Fe, no charge carriers are introduced in these intrinsic semiconductors. However, a change in lattice parameters, expressed in an elongation of the c/a lattice parameter ratio with minimal change in unit cell volume, reveals the existence of a three-stage cation restructuring process of Cu, Zn, and Fe. The resulting local anisotropic structural disorder leads to phonon scattering not normally observed, resulting in an effective approach to reduce th…
Electron–phonon effects on the direct band gap in semiconductors: LCAO calculations
2002
Abstract Using a perturbative treatment of the electron–phonon interaction, we have studied the effect of phonons on the direct band gap of conventional semiconductors. Our calculations are performed in the framework of the tight-binding linear combination of atomic orbitals (LCAO) approach. Within this scheme we have calculated the temperature and isotopic mass dependence of the lowest direct band gap of several semiconductors with diamond and zincblende structure. Our results reproduce the overall trend of available experimental data for the band gap as a function of temperature, as well as give correctly the mass dependence of the band gap on isotopic. A calculation of conduction band in…
Rotating magnetic fields as a means to control the hydrodynamics and heat/mass transfer in the processes of bulk single crystal growth
1999
The report discusses the possibility of using different types of rotating magnetic fields (RMF) and combinations of these to control the hydrodynamics and heat/mass transfer in the processes of bulk semiconductor single crystal growth. Some factors contributing to the efficiency of RMF influence in different technologies are analysed. Their specific practical application is illustrated by some examples.
Band Alignments in InxGa1–xP/GaAs Heterostructures Investigated by Pressure Experiments
2000
6 páginas, 3 figuras.