Interfacial Thermal Transport in Top-Side Diamond Integrated AlGaN/GaN High Electron Mobility Transistors

Area of Science:

• Materials Science
• Semiconductor Physics
• Thermal Management

Background:

• AlGaN/GaN HEMTs are crucial for RF power amplifiers but face thermal management challenges.
• Power derating is often necessary to prevent overheating, limiting device performance.
• Top-side diamond heat spreaders offer a solution for efficient heat dissipation.

Purpose of the Study:

• To investigate the thermal boundary resistance (TBR) introduced by a SiO2 interlayer during diamond heat spreader integration on AlGaN/GaN HEMTs.
• To quantify the contributions of the SiO2 interlayer and the AlGaN barrier to the overall TBR.
• To provide thermal modeling and design guidelines for optimizing diamond heat spreader integration.

Main Methods:

• Deposition of a polycrystalline diamond heat spreader on an AlGaN/GaN-on-SiC wafer using a 9.7 nm SiO2 interlayer.
• Measurement of total TBR as a function of temperature using time-domain thermoreflectance (TDTR).
• Thermal modeling of a multifinger AlGaN/GaN HEMT to assess cooling effectiveness.

Main Results:

• A room temperature TBR of 15.8 ± 1.44 m²K GW⁻¹ was measured, dominated by the SiO2 interlayer.
• A significant contribution from the AlGaN barrier to TBR was identified.
• TBR slightly decreased with increasing temperature due to the enhanced thermal conductivity of amorphous SiO2.

Conclusions:

• The SiO2 interlayer is a primary factor limiting heat transfer in diamond-integrated AlGaN/GaN HEMTs.
• The AlGaN barrier also contributes to TBR, becoming more significant as interlayer thickness decreases.
• Thermal modeling provides essential design guidelines for optimizing diamond heat spreader integration and device performance.