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.
Two-dimensional hydrodynamic model including inertia effects in carrier momentum for power millimetre-wave semi-conductor devices
Abstract A two dimensional-hydrodynamic model is carried out to predict the performance of short gate length power field effect transistors based on III–V semi-conductor systems. The model is based on the conservation equations, deduced from the Boltzmann transport equation, solved in their whole form by taking temporal and spatial variations in carrier momentum into account. This model is well suited to get accurate predictions for power devices having various gate recess topologies. Results are performed for devices with different gate lengths and compared with those obtained from simplified models. For gate lengths shorter than 0.5 μm, a drop in the overshoot velocity phenomenon involves a better estimation of the characteristics of the device.
Thermal resistance calculation of AlGaN/GaN on SiC devices
We present an original, accurate, closed-form expression for the thermal resistance of multifingers AlGaN/GaN on SiC FET devices. The model takes into account the thickness of GaN and SiC layers, the gate pitch, length, and width. The model's validity is verified by comparing it with the results of numerical simulations for many different devices. Very close (1-2%) agreement is observed in general. The model is also compared with experimental observations.