Strain-Reduction Induced Rise in Channel Temperature at Ohmic Contacts of GaN HEMTs

Abstract

Operating temperature distributions in AlGaN/GaN gateless and gated devices are characterized and analyzed using the InfraScope temperature mapping system. For the first time, a substantial rise of channel temperature at the inner ends of ohmic contacts has been observed. Synchrotron radiation-based high-resolution X-ray diffraction technique combined with drift–diffusion simulations show that strain reduction at the vicinity of ohmic contacts increases electric field at these locations, resulting in the rise of lattice temperature. The thermal coupling of a high conductive tensile region at the contacts to a low conductive channel region is an origin of the temperature rise observed in both short- and long-channel gateless devices.