Benchmarking of Thermal Boundary Resistance in AlGaN/GaN HEMTs on SiC Substrates: Implications of the Nucleation Layer Microstructure

A thermal boundary resistance (TBR) is associated with the presence of an AlN nucleation layer (NL) in AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on SiC substrates, raising device temperature beyond what is expected from the simple thermal conductivities of the main device layers. TBR was found to differ by up to a factor of four between different device suppliers, all using standard metal-organic chemical vapor deposition (MOCVD) growth techniques, related to the detailed NL microstructure. Optimizing the NL crystalline structure in MOCVD could therefore significantly improve heat extraction from AlGaN/GaN HEMTs into the SiC substrate, potentially reducing peak channel temperature rise by up to 40%, significantly benefiting device reliability.