Enhancement of Thermal Transfer From β-Ga2O3 Nano-Membrane Field-Effect Transistors to High Thermal Conductivity Substrate by Inserting an Interlayer

The role of a HfO 2 or ZrO 2 interlayer as a thermal bridge between a \beta -Ga 2 O 3 channel and a sapphire substrate was investigated using a \beta -Ga 2 O 3 nano-membrane FET as a test vehicle. A 35% less channel temperature increase was observed when a thin HfO 2 or ZrO 2 interlayer was inserted between the \beta -Ga 2 O 3 channel and the sapphire substrate compared to devices without interlayers. Phonon density of states (PDOS) mismatch can explain the improvement of the thermal boundary conductance (TBC). In the acoustic region, the PDOS of HfO 2 or ZrO 2 has about a 700% larger overlap area with the PDOS of \beta -Ga 2 O 3 compared to the PDOS of sapphire. This suggests that the insertion of a thermal bridge interlayer can provide a potential solution to the low thermal conductivity of \beta -Ga 2 O 3 and the self-heating effect of \beta -Ga 2 O 3 -based FETs.