Recent Advances in GaN‐Based Power HEMT Devices

Structural, electrical and magnetic properties of (Cd, Ti) modified BiFeO 3

Synthesis and characterizations of Ag-doped CdO nanoparticles for P-N junction diode application

The MnWO4 nanorods were successfully synthesized by surfactant assisted ultrasonics method and characterized its structural (XRD), morphological (SEM) electrical (solid state impedance) and electrochemical (CV) properties. The X-ray diffraction patterns inferred the formation of highly crystalline monoclinic structure of MnWO4. The formation of nanorods with the aspect ratios of 30–40 nm were reveals from SEM image. The maximum d.c. electrical conductivity was found to be 4.40 × 10−5 S/cm at 570°C for MnWO4 nanorods prepared by surfactant assisted ultrasonic method. The quasi-rectangular behavior of cyclic voltammogram inferred the supercapacitive behavior of the prepared MnWO4 nanorods.

Synthesis of MnWO4 nanorods and its electrical and electrochemical properties

In the present communication, studies of some physical properties (i.e., crystal data, permittivity, impedance, electrical cobnduction and magnetic) of a multiferroic material with a chemical composition (SmLi)1/2(Fe2/3Mo1/3)O3 have been reported. Thermogravimetric analysis of the compound, prepared by cost effective ceramic technology processing, was executed to check the mass loss as well as the required decomposition temperature of the ingredients. An analysis of X-ray spectra or pattern suggests that the crystallization phase or cystal system of the compound at room temperature is orthorhombic. The broad studies of dielectric properties {relative dielectric constant (er), and tangent loss (tan δ)} display their independence of temperature and frequency in the rage of (30–375 °C) and (1 kHz–1 MHz) respectively. The impedance spectroscopic technique has provided a considerable significant information regarding the grain, grain boundary contribution within the sample and relaxation mechanism of the compound. The occurrence of negative temperature coefficient behaviour (NTCR) is depicted by the further analysis of impedance parameters. The frequency–temperature dependence of conductivity follows the Johnson’s power Universal law. The Arrhenius plot (i.e., variation of electrical conductivity with temperature) is used to calculate the activation energy. Analysis of magnetization (M–H) loop shows weak ferromagnetism of the compound. The material possesses significantly high magnitude of magnetoelectric coefficient of 3.0 mV Cm− 1 Oe− 1.

Studies of structural, impedance spectroscopy and magnetoelectric properties of (SmLi) 1/2 (Fe 2/3 Mo 1/3 )O 3 electroceramics

We have demonstrated the potential use of thermally grown TiO2 and Al2O3 oxides as gate dielectrics for GaN-based high-electron-mobility-transistors. TiO2 and Al2O3 are found to provide negative and positive band offsets with AlGaN, respectively. A significant performance improvement on various device characteristics provides evidence for its potential use. The oxides are formed by a combination of predeposition of a thin film and followed by oxidation in pure O2 environment. The formation and thickness of the oxides are confirmed through the X-ray photoelectron spectroscopy and the transmission electron microscopy. The performance improvement for TiO2- and Al2O3-based oxide gates have been identified in terms of a ideality factor and a reduction in the gate leakage current in comparison with that of control devices. This is further augmented by an increase in the ${n}_{s}\times \mu $ product. The ON/OFF current ratio and turn-ON voltage increase by 2–3 orders of magnitude and 0.3–0.6, respectively, for the Schottky diodes. The negative shift on the capacitance–voltage characteristics is also found to be minimal, indicating higher gate coupling with thermally grown oxides.

Thermally Grown TiO 2 and Al 2 O 3 for GaN-Based MOS-HEMTs

In this letter, we have reported a novel metal scheme Ti/Au/Al/Ni/Au for ohmic contact on AlGaN/GaN high-electron-mobility transistors. The reported metal scheme is observed to show minimum metal out-diffusion and sharp edge acuity at high-temperature annealing, which facilitates aggressive scaling of source–drain separation ( ${L} _{\textsf {SD}}$ ). We have demonstrated ${L} _{\textsf {SD}}$ as low as 300 nm with gate length ( ${L} _{\textsf {g}}$ ) of 100 nm for this metal stack. We observed improvement in ON-resistance ( ${R} _{\mathrm{\scriptscriptstyle ON}}$ ) from 3 to $1.25~\Omega \cdot$ mm, transconductance ( ${g} _{\textsf {m}}$ ) from 276 to 365 mS/mm, saturation drain current ( ${I} _{\textsf {DS,sat}}$ ) from 906 to 1230 mA/mm, and unity current gain frequency ( ${f} _{\textsf {T}}$ ) from 70 to 93 GHz by scaling ${L} _{\textsf {SD}}$ from $3~\mu \text{m}$ to 300 nm. The gate lengths for all devices were 100 nm.

Ti/Au/Al/Ni/Au Low Contact Resistance and Sharp Edge Acuity for Highly Scalable AlGaN/GaN HEMTs

This work demonstrates the low temperature thin-film deposition of silicon nitride ( SiN x) for III-nitride-based high electron mobility transistors using inductively coupled plasma chemical vapor deposition. It is observed that the nonlinear dependency of the deposition temperature and gas flow rates have a profound impact on the film quality. The process parameter space is scanned and the optimum film quality is achieved, which is verified with physical and electrical characterizations. The best quality film is achieved at a deposition temperature of 380  °C demonstrating near ideal stoichiometry with negligible hydrogen ( <5%) and oxygen ( <3%) concentrations. In addition, the optimized film is found to have zero pinholes even at a thickness of 10 nm and is uniform over a large area with an rms roughness of 0.58 nm. The deposited films are characterized by atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The dielectric strength and dielectric constant of these films are determined from current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the metal-insulator-metal structure, respectively. For the best quality film, the values of dielectric strength and dielectric constant are measured to be ∼ 8 MV/cm and ∼ 7.5, respectively. A metal-insulator-semiconductor-heterostructure (metal/SiN x/AlGaN/GaN) capacitor is fabricated with the optimized recipe for interface characterization. The density of slow traps is determined from the hysteresis in the C-V curve and found to be 7.38 × 10 10 cm − 2. The frequency dependent conductance method is also used to investigate the trap density. The trap state density is found to be 1.67 × 10 12 cm − 2 eV − 1 at 0.29 eV below conduction band.

Yogendra K. Yadav

Papers

Thermally Grown TiO 2 and Al 2 O 3 for GaN-Based MOS-HEMTs

Ti/Au/Al/Ni/Au Low Contact Resistance and Sharp Edge Acuity for Highly Scalable AlGaN/GaN HEMTs

Realization of high quality silicon nitride deposition at low temperatures

Reduced Contact Resistance and Improved Transistor Performance by Surface Plasma Treatment on Ohmic Regions in AlGaN/GaN HEMT Heterostructures

Electrical properties of Bi2TiO5 ceramic