PROJECT TITLE :

Thermal Characterization Using Optical Methods of AlGaN/GaN HEMTs on SiC Substrate in RF Operating Conditions

ABSTRACT:

Performance and reliability of wide bandgap high-power amplifiers are correlated with their thermal behavior. Thermal model development and appropriate temperature measurement systems are necessary to quantify the channel temperature of devices in real operating conditions. As a direct temperature measurement at intervals a channel is normally not achievable, the common approach is to measure the device temperature at completely different locations shut to the hotspot and then to use simulations to estimate the channel temperature. This paper describes a whole thermal characterization of AlGaN/gallium nitride (GaN) on silicon carbide high electron-mobility transistors (HEMTs) when devices are operating in dc bias, pulsed, and continuous wave. Infrared thermography, charge-coupled device-based thermoreflectance microscopy, and micro-Raman spectroscopy are performed to extract the thermal resistance of the elements. Results are compared with simulations employing a three-D finite-element model to estimate the operating channel temperature. Measurements have shown that the RF-biased thermal resistance and therefore the dc-biased thermal resistance of GaN HEMTs are similar.