Thermal Characterization and Design of AlN/GaN/AlN HEMTs on Foreign Substrates

AlN/GaN/AlN high electron mobility transistors (HEMTs) offer enhanced carrier confinement and higher breakdown voltage than conventional AlGaN/GaN HEMTs. In this work, Raman thermometry was used to characterize the self-heating behavior of a single-finger AlN/GaN/AlN HEMT on 6H-SiC. A 3D finite element analysis model was created to optimize the thermal design of the device structure. Simulation results reveal that the optimal buffer layer thicknesses to minimize the channel temperature rise of AlN/GaN/AlN HEMTs on 6H-SiC and diamond substrates are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 2~\mu $ </tex-math></inline-formula>m and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 0.7~\mu $ </tex-math></inline-formula>m, respectively. Moreover, diamond substrate integration further enhances the thermal performance, achieving a ~45% and ~53% reduction in the device thermal resistance as compared to those of an AlN/GaN/AlN HEMT on 6H-SiC and an AlGaN/GaN HEMT on 4H-SiC, respectively.