Physical study of the dissipated power area in high electron mobility transistors for thermal modelling
The hot area in power transistors due to the power dissipation is determined from a 2D-hydrodynamic model. The power is calculated everywhere in the device from the knowledge of the physical quantities (current density, electric field). The hot area is determined accurately to be coupled to a thermal modelling giving the temperature everywhere in the device [J. Park, M.-W Shin, C.-C. Lee, Thermal modeling and measurement of GaN-based HFET devices, IEEE Electron Device Lett. 24(7) (2003) 424-426 [1]; J.-C Jacquet, R. Aubry, H. Gerard, E. Delos, N. Rolland, Y. Cordier, A. Bussutil, M. Rousseau, S.L. Delage, Analytical transport model of AlGaN/GaN HEMT based on electrical and thermal measurement, 12th GAAS Symposium, Amsterdam, 2004, pp. 235-238 [2].]. The method is applied to HEMTs (high electron mobility transistors) based on GaAs or GaN. It is shown that the hot area depends on the bias conditions and on the transistor gate recess topology.
Comparison of wurtzite and zinc blende III–V nitrides field effect transistors: a 2D Monte Carlo device simulation
Abstract An ensemble Monte Carlo method is used to compare the potentialities of zinc blende and wurtzite GaN for field effect transistor applications. First, bulk material electron transport properties are compared and we find that mobility, steady state velocity and velocity overshoot are at the advantage of zinc blende GaN. Then, zinc blende GaN and wurtzite GaN MESFET with very short gate length (Lg=0.12 μm) are investigated using a 2D Monte Carlo device simulation. A 50% gain in performance is obtained for the zinc blende GaN MESFET as compared with the wurtzite one. A zinc blende AlGaN/GaN HEMT is also simulated and exhibits a current density of 900 mA mm−1, a transconductance of 480 mS mm−1 and a cut-off frequency of 180 GHz.
Substation automation based on IEC 61850 with new process-close technologies
New technologies in primary equipment like nonconventional instrument transformers require new interfaces to the substation automation system. The future standard IEC 61850 perfectly supports this requirement. With the introduction of the new technologies and the use of IEC 61850, a more decentralized architecture of the substation automation system will be possible. This provides several benefits but a careful system design is required to maintain the overall reliability of the system.