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The electron mobility limited by different scattering mechanisms in the quaternary AlInGaN alloy grown on a GaN layer is investigated with the classical Hall measurement, which is performed at a temperature range of 12 and 350 K and a magnetic field of B = 0.51 T. The effect of the thickness and alloy composition of the quaternary AlInGaN layer on the mobility is also determined. The experimentally determined temperature-dependent Hall mobility was compared with mobility calculated by using Matthiessen's rule. The main scattering mechanisms, including acoustic phonon scattering (piezoelectric and deformation potential), polar optical phonon scattering, alloy disorder scattering, interface roughness scattering, ionized impurity scattering, dislocation scattering, background impurity scattering, were used in the calculations for all temperatures. The results show that the dominant scattering mechanisms, depending on the investigated sample, are the interface roughness scattering and alloy disorder scattering at almost all temperatures. At a low-temperature, mobility is limited by ionized impurity scattering. High-temperature mobility is limited by polar optical phonon scattering. Furthermore, our results suggest that the thickness and alloy composition of the quaternary AlInGaN layer should be optimized for better transport properties.

Hall effect is a very popular technique and is widely used to quantify important electrical parameters such as carrier concentration, resistivity, mobility and Hall coefficient of different types of samples. In this paper, electrical characteristics of three ceramic samples will be analyzed using a Hall effect measurement system (Ecopia, HMS-3000), which is based on the van der Pauw method. Measured results for mobility and electrical resistivity at three temperatures (25?C, 50?C and 80?C) will be presented. Current-voltage and current-resistance dependence between terminals of four point contact of different samples will be also demonstrated.

Two AlInN/AlN/GaN heterostructures with 280-nm- and 400-nm-thick AlN buffer grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) have been investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and Hall-effect measurements. The symmetric (0002) plane with respect to the asymmetric (10 $$\bar{1}$$ 2) plane in the 280-nm-thick AlN buffer has a higher crystal quality, as opposed to the 400-nm-thick buffer. The thinner buffer improves the crystallinity of both (0002) and (10 $$\bar{1}$$ 2) planes in the GaN layers, it also provides a sizeable reduction in dislocation density of GaN. Furthermore, the lower buffer thickness leads to a good quality surface with an rms roughness of 0.30 nm and a dark spot density of 4.0 × 108 cm−2. The optical and transport properties of the AlInN/AlN/GaN structure with the relatively thin buffer are compatible with the enhancement in its structural quality, as verified by XRD and AFM results.

The Hall and effective mobility characteristics of n-type junctionless transistors (JLTs) at low temperature (T=100K) are reported here for the first time. To this end, the effective mobility values (μEff) were extracted from the charge based analytical model of JLT with account for flat-band (VFB) position and split capacitance-to-voltage (CV), respectively. Besides, in order to directly determine the surface carrier density (NS) and corresponding Hall mobility (μHall), Hall Effect measurements were carried out and compared to μEff. Keywords-Junctionless transistor, Hall Effect measurement, Split CV measurement, Mobility, Flat-band voltage.

Hall effect measurements of a graphene-on-SiC system were carried out as a function of temperature (1.8-200 K) at a static magnetic field (0.51) With the analysis of temperature dependent single-field Hall data with the Simple Parallel Conduction Extraction Method (SPCEM), bulk and two-dimensional (2D) carrier densities and mobilities were extracted successfully. Bulk carrier is attributed to SIC substrate and 2D carrier is attributed to the graphene layer. For each SPCEM extracted carrier data, relevant three-dimensional or 2D scattering analyses were performed. Each SPCEM extracted carrier data were explained with the related scattering analyses. A temperature independent mobility component, which may related to an interaction between graphene and SIC, was observed for both scattering analyses with the same mobility limiting value. With the SPCEM, effective ionized impurity concentration of SiC substrate, extracted 2D-mobility, and sheet carrier density of the graphene layer are calculated with using temperature dependent static magnetic field Hall data. Funding Agencies|DPT-HAMIT; DPT-FOTON; TUBITAK [113F364, 113E331, 109A015, 109E301]; Turkish Academy of Sciences; [NATO-SET-193]

WOS: 000314724500045, Shubnikov-de Haas (SdH) and Hall effect measurements performed in a temperature range between 1.8 and 275 K, at an electric field up to 35 kV m(-1) and magnetic fields up to 11 T, have been used to investigate the electronic transport properties of monolayer graphene on SiC substrate. The number of layers was determined by the use of the Raman spectroscopy. The carrier density and in-plane effective mass of electrons have been obtained from the periods and temperature dependencies of the amplitude of the SdH oscillations, respectively. The effective mass is in good agreement with the current results in the literature. The two-dimensional (2D) electron energy relaxations in monolayer graphene were also investigated experimentally. The electron temperature (T-e) of hot electrons was obtained from the lattice temperature (T-L) and the applied electric field dependencies of the amplitude of SdH oscillations. The experimental results for the electron temperature dependence of power loss indicate that the energy relaxation of electrons is due to acoustic phonon emission via mixed unscreened piezoelectric interaction and deformation-potential scattering

Polycrystalline InxGa1-xN thin films were prepared by mixed source modified activated reactive evaporation (MARE) technique. The films were deposited at room temperature on glass substrates without any buffer layer. All the films crystallize in the hexagonal wurtzite structure. The indium concentration calculated from XRD peak shift using Vegard's law was found to be varying from 2% to 92%. The band gap varies from 1.72 eV to 3.2 eV for different indium compositions. The indium rich films have higher refractive indices as compared to the gallium rich films. The near infra-red absorption decreases with gallium incorporation into InN lattice which is mainly due to decrease in the free carrier concentration in the alloy system. This fact is further supported from Hall effect measurements. MARE turns out to be a promising technique to grow InxGa1-xN films over the entire composition range at room temperature. � 2011 Elsevier B.V. All rights reserved.

In this work, nanocrystalline lead telluride powder was synthesized from high-purity elements by mechanical alloying by means of a planetary ball-milling procedure. The milling medium was tungsten carbide, and the diameter of the balls was varied in order to investigate the effect on the structural features of the material. Phase transformations and crystallite evolution during ball-milling were followed by powder x-ray diffraction (PXRD). The broadened PXRD peaks were analyzed with Voigt functions, revealing small crystalline size and stress introduced during the mechanical alloying process. Transmission electron microscopy (TEM) studies confirmed the material's nanostructure, as well as the effect of ball diameter on the size of the crystals. Thermoelectric properties are discussed in terms of the Seebeck coefficient and the nominal carrier concentration, as determined by Hall-effect measurements. The enhancement of the Seebeck coefficient is reported to be higher compared with other PbTe-based nanocomposites. © 2010 TMS. 39 1665 1668 1665-1668