Thermal modeling, measurements and design considerations of GaAs microwave devices

This paper addresses the thermal management issues associated with fabricating microwave power devices. Thermal management of microwave devices includes: modeling thermal resistance with techniques such as Green´s function/method of images, conformal map, finite element, spectral domain, and Fourier series; measurement techniques such as improved IR, self heating, laser probing, and direct thermocouple measurement; and layout and fabrication alternatives such as silicon substrates, shunt metal paths, and selective thinning that allow smaller form factors while maintaining or reducing thermal resistance. Examples of several device layout and fabrication approaches (MESFET, HBT, PHEMT) show how high frequency performance and low thermal resistance can be part of the unit cell design.