Thermal Transport in Superlattice Castellated Field Effect Transistors

Heat extraction from novel GaN/AlGaN superlattice castellated field effect transistors developed as an RF switch is studied. The device thermal resistance was determined as 19.1 ± 0.7 K/(W/mm) from a combination of Raman thermography measurements, and gate resistance thermometry. Finite element simulations were used to predict the peak temperatures and show that the three-dimensional gate structure aids the extraction of heat generated in the channel. The calculated heat flux in the castellations shows that the gate metal provides a high thermal conductivity path, bypassing the lower thermal conductivity superlattice, reducing channel temperatures by as much as 23%.