Thermal characterization and modelling of a gallium arsenide power amplifier MMIC

Thermal characterization of high power microwave devices is important for determining their reliability. Exceeding the optimal temperature will have a detrimental effect on the performance and reliability of these devices. However, temperature characterization of submicron features is often challenging and numerical simulations are often used. In this paper, a detailed finite element thermal model of a power amplifier Monolithic Microwave Integrated Circuit (MMIC) was developed and analyzed to obtain the peak operating junction temperature. Although detailed models would give more accurate results, they usually require more computational effort and time. Hence, a simplified finite element thermal model was also developed and its results compared with those for the detailed model. It was found that the results from the simplified model are higher than those from the detailed model by about 3°C to 8°C at 1W/mm and 1.5W/mm respectively. The temperature distributions of actual power amplifier MMIC devices were measured using IR thermography and thermoreflectance (TR) thermography. It was found that the temperature measured using TR thermography agreed very well with the FEA results but those obtained using IR thermography did not.