Channel temperature estimation in GaAs FET devices

Operating channel temperature has an important influence on the electrical performance and reliability of GaAs FET amplifiers but this parameter is difficult to determine experimentally or analytically. Simplified closed-form and numerical models are commonly used although both are subject to errors in the case of sub-micron heat sources surrounded by epitaxial layers. Some assumptions about the heat source size and location are explored using finite-difference simulation. A simple measurement technique making use of the temperature coefficient of gate metal resistance is described, and an improved procedure for spatial averaging correction of infrared measurements of sub-micron heat sources is proposed.