Double Leakage Research Articles

Limitations of Field Plate Effect Due to the Silicon Substrate in AlGaN/GaN/AlGaN DHFETs

We investigated the limitations of the field plate (FP) effect on breakdown voltage <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BD</sub> that is due to the silicon substrate in AlGaN/GaN/AlGaN double heterostructures field-effect transistors. In our previous work, we showed that in devices with large gate-drain distance (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> > 8 μm), the breakdown voltage does not linearly increase with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> because of a double leakage path between the silicon substrate and the metal contacts, which makes the device break at the silicon interface. In this paper, we showed that the effect of the FP for such large <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> is not significant because the breakdown is still dominated by the silicon substrate. The increase in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BD</sub> due to the FP is significant only for devices with small gate-drain distances ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> <; 8 μm). Indeed we show that for such small <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> the increase in the breakdown voltage is more than double, whereas for larger <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> , this is only about 10%. Simulations of AlGaN/GaN/AlGaN devices for small <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> are carried out with different FP lengths and passivation thickness in order to study the electric field distribution.

CONDUCTION CHARACTERISTICS OF Na-β(β")-Al2O3 CONTAINING FINE CARBON PARTICLES

The conduction charateristics of Na-β(β″)-Al2O3 containing (1-10wt%) fine carbon particles have been investigated. The study shows that the samples containing less than 6 wt% of carbon are still fast ionic conductors and their conductivity is one to two orders of magnitude higher than that of pure Na-β(β″)-Al2O3. The electrical parameters of the samples, such as the bulk resistance, grain boundary resistance, double layer capacitance and leakage current resistance vary with content of carbon. These influences of carbon have been discussed here in some detail. The measurement of conductivity in temperature range from -40℃ to 80℃ shows that Na-β(β″)-Al2O3 containing less than 6 wt% of carbon are good materials for making double layer capacitor.