Electric Properties of AlGaN/GaN/Si High Electron Mobility Transistors

This work investigated the electrical properties in AlGaN/GaN/Si HEMTsgrown by molecular beam epitaxy. The electrical behavior have been investigated using by electric permittivity, modulus formalism and conductance measurements. As has been found from electrical conductance, dispersive behavior is related to barrier inhomogeneity and deep trap in barrier layer. On the other hand, the strain relaxation of charge transport is studied both permittivity and electric modulus formalisms.

Influence of Grain and Grain Boundary Interfaces on Dielectric Relaxation of Ceria Nanocrystals Using Modulus Formalism Under Biased and Equilibrium Conditions

Dielectric relaxation of ceria nanocrystals under biased condition for different grain sizes was in this study evaluated in modulus formalism using impedance spectroscopy. Prior to the impedance measurements, the ceria sample was calcined at 200 °C for 30 min and pressed into cylindrical pellets with 8 mm diameter and 1 mm thick by applying uniaxial four-ton pressure using a hydraulic press. This was then sintered at 300 °C, 450 °C, 600 °C and 900 °C for 30 min. Systematic analysis of modulus formalism data using commercial Z-view and Z-plot software's permitted, reliable extraction of dielectric relaxation time (τ) of ceria nanocrystals. The observed dielectric relaxation time (τ) at equilibrium condition varied from 10–5 to 10–3 s when the grain size of ceria nanocrystals was increased from 9 nm to 29 nm. But when the DC bias voltage was applied, the same dielectric relaxation time (τ) was tuned to ∼10–4 s for all the grain sizes of ceria nanocrystals, because of Schottky grain boundary potential barrier height (φb) suppression.

STRUCTURAL AND DIELECTRIC PROPERTIES OF GLASSES IN THE SYSTEM TeO2–CaCu3Ti4O12

The glasses in the system (100 - x) TeO2 –x CaCu3Ti4O12 , (x = 0.25 mol. % to 3 mol.%) were fabricated. The color varied from olive green to brown as the CaCu3Ti4O12 (CCTO) content increased in TeO2 matrix. The X-ray powder diffraction and differential scanning calorimetric analyses that were carried out on the as-quenched samples confirmed their amorphous and glassy nature respectively. The dielectric constant and loss in the 100 Hz–1 MHz frequency range were monitored as a function of temperature (50–400°C). The dielectric constant [Formula: see text] and the loss (D) increased as the CCTO content increased in TeO2 at all the frequencies and temperatures under investigation. Further, the [Formula: see text] and D were found to be frequency-independent in the 50–200°C temperature range. The value obtained for the loss at 1 MHz was 0.0019 which was typical of low loss materials, and exhibited near constant loss (NCL) in the 100 Hz–1 MHz frequency range. The electrical relaxation was rationalized using the electric modulus formalism. These glasses may be of considerable interest as substrates for high frequency circuit elements in conventional semiconductor industries owing to their high thermal stability.