A Novel Strategy for GaN-on-Diamond Device with a High Thermal Boundary Conductance

TL;DR

This paper presents a new bonding strategy using surface activated bonding and high-temperature annealing to create GaN-on-diamond devices with enhanced thermal boundary conductance, improving heat dissipation for high-performance GaN-based transistors.

Contribution

It introduces a novel SAB method with silicon interlayers and annealing to significantly increase thermal boundary conductance in GaN-diamond composites.

Findings

Higher TBC achieved with 15 nm Si interlayer before annealing.

Post-annealing increases TBC, especially with 22 nm Si interlayer.

High thermal stability with stress below 230 MPa.

Abstract

To achieve high device performance and high reliability for the gallium nitride (GaN)-based high electron mobility transistors (HEMTs), efficient heat dissipation is important but remains challenging. Enormous efforts have been made to transfer a GaN device layer onto a diamond substrate with a high thermal conductivity by bonding. In this work, two GaN-diamond bonded composites are prepared via modified surface activated bonding (SAB) at room temperature with silicon interlayers of different thicknesses (15 nm and 22 nm). Before and after post-annealing process at 800 oC, thermal boundary conductance (TBC) across the bonded interface including the interlayer and the stress of GaN layer are investigated by time-domain thermoreflectance and Raman spectroscopy, respectively. After bonding, the 15 nm Si interlayer achieved a higher TBC. The post-annealing significantly increased the TBC of both interfaces, while the TBC of 22 nm silicon interlayer increased greater and became higher than that of 15 nm. Detailed investigation of the microstructure and composition of the interfaces were carried out to understand the difference in interfacial thermal conduction. The obtained stress was no more than 230 MPa for both before and after the annealing, and this high thermal stability of the bonded composites indicates that the room temperature bonding can realize a GaN-on-diamond template suitable for further epitaxial growth or device process. This work brings a novel strategy of SAB followed by high-temperature annealing to fabricate a GaN-on-diamond device with a high TBC.