Thermal Characterization of GaN Power HEMTs by Transient <i>I</i> – <i>V</i> Curves, Infrared Microscopy, and Thermal Simulation

This work investigates the thermal characteristics of gallium nitride (GaN) high-electron mobility transistors (HEMTs) for power applications. Exemplarily, a 650-V class HEMT is analyzed by different thermal characterization methods such as transient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I$</tex-math> </inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$</tex-math> </inline-formula> measurements, infrared (IR) microscopy, and simulations, presenting a comprehensive insight into the thermal behavior. A new electrothermal model function is derived for the extraction of thermal parameters by transient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I$</tex-math> </inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$</tex-math> </inline-formula> measurements, and it is not limited to the linear region of the output characteristic, as a model presented in previous work, but also applicable in the saturation region. Fifth-order Foster model parameters are extracted for different operating points in linear and saturation regions. For verification and better understanding, the measurements are also performed by IR microscopy at same operating points enabling the characterization of the device’s surface temperature distribution. Two new analytical models allow the interpretation of the temperature distribution and are used as fit formulas for extracting the thermal parameters found by IR microscopy. Finally, the research includes an investigation using technology computer-aided design (TCAD) simulation, followed by a thermal 3-D finite element simulation. The results allow a deeper understanding of the electrothermal behavior of GaN power HEMTs at various operating points.