Transmission-line-matrix (TLM) modeling of self-heating in AlGaN/GaN transistor structures

Self-heating in AlGaN/GaN (GaN—gallium nitride) heterostructures is an important issue for a large use of these devices in high-density power telecommunication applications. The equation of heat associated with this type of problem does not admit an analytical solution. Hence, we propose a numerical solution based on the use of a transmission line matrix (TLM). The method is easy to program and gives insights on temperature distribution throughout the device. It allows a better understanding of heat behavior and management at each layer that forms the structure. Some TLM simulation results have been compared with those obtained experimentally using integrated micro-Raman/infrared (IR) thermography methods, and have been found to agree within the bounds set by the resolution of the meshes used. The TLM has also the advantage upon other numerical methods of being unconditionally stable, one step and can adapt to complex geometries such as devices with several fingers.