Effects of SiN passivation and high-electric field on AlGaN-GaN HFET degradation

The authors report on the effects of silicon nitride (SiN) surface passivation and high-electric field stress (hot electron stress) on the degradation of undoped AlGaN-GaN power HFETs. Stressed devices demonstrated a decrease in the drain current and maximum transconductance and an increase in the parasitic drain series resistance, gate leakage, and subthreshold current. The unpassivated devices showed more significant degradation than SiN passivated devices. Gate lag phenomenon was observed from unpassivated devices and removed by SiN passivation. However, SiN passivated devices also showed gate lag phenomena after high-electric field stress, which suggests possible changes in surface trap profiles occurred during high-electric field stress test.     

Efficient Design of Rounding Based Static Segment Imprecise Multipliers for Error Tolerance Application

Journal of Electronic Testing - Error-Tolerant applications regularly accomplish more data adaption. Approximate computing is one of the optimum strategies for data manipulation in several...     

Deformation Behavior of Metastable Austenitic Steel at Low and Moderate Temperatures

Metal Science and Heat Treatment - The TRIP effect and deformation behavior of metastable austenitic steel were studied under tension in the temperatures range from –120 to +200°C. The...     

Generalized analytical expressions for Tafel slope,reaction order and a.c. impedance for the hydrogen evolution reaction (HER): mechanism of HER on platinum in alkaline media

Following the generally accepted mechanism of the HER involving the initial proton discharge step to form the adsorbed hydrogen intermediate, which is desorbed either chemically or electrochemically, generalized expressions for the Tafel slope, reaction order and the a.c. impedance for the hydrogen evolution reaction are derived using the steady-state approach, taking into account the forward and backward rates of the three constituent paths and the lateral interactions between the chemisorbed intermediates. Limiting relationships for the Tafel slope and the reaction order, previously published, are deduced from these general equations as special cases. These relationships, used to decipher the mechanistic aspects by examining the kinetic data for the HER on platinum in alkaline media, showed that the experimental observations can be consistently rationalized by the discharge-electrochemical desorption mechanism, the rate of the discharge step being retarded on inactive platinum compared to the same on active platinum.Nomenclature C _d double-layer capacity (µF cm^–2) - E _rev reversible electrode potential (V) - F Faraday number (96 487 C mol^–1 ) - R gas constant - T temperature (K) - Y _f Faradaic admittance (^–1 cm^–2) - Y _t Total admittance (^–1 cm^–2) - Z _f Faradaic impedance ( cm²) - i _f total current density (A cm^–2) - i _nf nonfaradaic current density (A cm^–2) - j - k ₀ ¹ rate constant of the steps described in Equations 1 to 3 (mol cm^–2 s^–1 ) - j - qmax saturation charge (µC cm^–2) - Laplace transformed expressions for i, and E - _{1 3} symmetry factors for the Equations 1 and 3 - saturation value of adsorbed intermediates (mol cm^–2) - overpotential - coverage by adsorbed intermediates - angular frequency This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday, and in recognition of his outstanding contribution to electrochemistry.     

GaN based high temperature strain gauges

Gallium Nitride based electronic devices have several unique properties such as robustness to high temperature, and both strong spontaneous and piezoelectric polarization fields. The polarization effects of Gallium Nitride are stable at high temperatures; therefore, it is an ideal material to fabricate high temperature strain gauges. In this work we have fabricated metal-insulator-semiconductor(MIS) capacitors to be used as a high temperature strain gauge. GaN based MIS capacitors were fabricated and tested both at room and high temperature. The gauge factor was measured to be 75 at room temperature. AlGaN/GaN heterostructures were also used to make MIS capacitors for testing at both room and high temperature. The gauge factors were measured on these devices to be 575 at room temperature, and 361 at 400 °C.     

Estimation of current efficiency in ion-exchange membrane chlor-alkali cells

A generalized current efficiency equation was derived from material balance considerations to estimate the caustic current efficiency in ion exchange chlor-alkali membrane cells taking into account the presence of NaHCO₃, Na₂CO₃, and NaOH in the feed brine. The validity and the accuracy of this equation was established by comparing the ‘gas analysis’ results with the data obtained from caustic collection measurements. It is also shown that this general expression can be easily extended to deduce the current efficiency applicable for diaphragm cell operations.     

A Rotor Condition Monitor for Squirrel-Cage Induction Machines

Rotor temperature is of concern in both short-term machine protection and in longer term condition monitoring systems for large induction machines. Unduly large temperatures can arise under severe operating conditions such as stall and overload. A cage rotor condition monitoring system using direct temperature measurement is described. Under running conditions, it continuously transmits temperature information about strategic points on the rotor via an optical link. Possible rotor circuit imperfections are broken bars and end rings, single or multiple, and the deterioration of bar/end ring joints. The possibility of using temperature information for the identification of these faults is also investigated.