Joint Use of Thermal Characterization and Simulation of AlGaN/GaN High-Electron Mobility Transistors in Transient and Steady State Regimes to Estimate the Hotspot Temperature

Channel temperature has a strong impact on the performance of a microwave power transistor. In this paper, various methods, including electrical measurements, optical analysis, and FEM simulations, were employed to perform both transient and steady-state thermal characterization of GH15 2 × 150 µm transistors from UMS foundry (United Monolithic Semiconductors, France). The transient study allowed for the extraction of thermal time constants according to which the temperature in the transistor changes. The steady-state study provided the hotspot temperature. As the channel is physically inaccessible, direct thermal measurement at the hotspot is not possible, in order to extract the temperature of this hotspot, different measurement methods are combined by simulation, which is calibrated based on the measurements, resulting in a well-adjusted thermal model. This calibrated model enabled the extraction of temperature at any location within the device’s structure, particularly at the hotspot. The measurement and simulation results have shown that the hotspot temperature can be 30% higher than the temperature of the nearest external surface for high dissipated power levels.