Analysis of Thermal Effect Influence in Gallium-Nitride-Based TLM Structures by Means of a Transport–Thermal Modeling

The power dissipation in a semiconductor device usually generates a self-heating effect, which becomes very significant for gallium nitride power applications. The operating temperature of these devices increases significantly, and the transport properties are then degraded (IEEE Electron Device Lett., vol. 24, p. 375, 2003; IEEE Electron Device Lett., vol. 49, p. 1496, 2002; IEEE Trans. Electron Devices, vol. 52, p. 1683, 2005). Taking heating effects into account explains the physical phenomena observed in experiments, due in particular to the fact that temperature greatly affects the velocity. In this paper, numerical simulations are carried out to study the influence of thermal effects on the static characteristics of GaN transmission line measurement (TLM) model structures. A transport-thermal model is thus developed in order to take into account both the electrical and the thermal phenomena in a coupled way. This paper uses GaN TLMs on sapphire substrates. Simulations have shown that the saturation current is reached for electric fields much lower than the saturation electric field, thus confirming the experimental results