Enhancement of Thermal Transfer From β-Ga<sub>2</sub>O<sub>3</sub> Nano-Membrane Field-Effect Transistors to High Thermal Conductivity Substrate by Inserting an Interlayer
Jinhyun Noh, Prabudhya Roy Chowdhury, Mauricio Segovia, Sami Alajlouni, Mengwei Si, Adam Charnas, Shouyuan Huang, Kerry Maize, Ali Shakouri, Xianfan Xu, Xiulin Ruan, Peide D. Ye
Abstract
The role of a HfO<sub>2</sub> or ZrO<sub>2</sub> interlayer as a thermal bridge between a <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> channel and a sapphire substrate was investigated using a <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> nano-membrane FET as a test vehicle. A 35% less channel temperature increase was observed when a thin HfO<sub>2</sub> or ZrO<sub>2</sub> interlayer was inserted between the <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> 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<sub>2</sub> or ZrO<sub>2</sub> has about a 700% larger overlap area with the PDOS of <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> 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 <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> and the self-heating effect of <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub>-based FETs.