Thermal analysis of aluminum gallium nitride/gallium nitride HEMT monolithic integration with CMOS on silicon (111) substrates

A thermal analysis of the potential monolithic integration of AlGaN/GaN HEMTs with CMOS in silicon substrates is performed. ATAR, an in-house 3-D thermal modeling tool, is used to perform a thermal analysis on a 300 mum wide GaN transistor in two different packages. Simulations ranging from 2 W/mm to 8 W/mm of dissipated power in the transistor suggest that the surrounding region experiences a slight thermal gradient, but will still be able to house CMOS circuitry with some careful design. Due to the high-resistivity silicon substrate, the local heating of the GaN HEMT is substantial, which is undesirable. A novel back-trenching technique, which can lower the device maximum temperature by 100 K is proposed. The potential for modeling the thermal transient behavior using an RC network is also demonstrated.