Monolithic integration of diverse crystalline thin films on diamond for near-junction thermal management

TL;DR

This paper presents a scalable method for monolithically integrating diverse crystalline thin films on diamond, achieving ultrahigh interfacial thermal conductance to improve thermal management in high-power RF devices.

Contribution

It introduces a multi-step transfer printing technique for integrating multiple crystalline films on diamond and demonstrates ultrahigh interfacial thermal conductance at the ta-Ga2O3/diamond interface.

Findings

Achieved an interfacial thermal conductance of 149 MW/m^2K at ta-Ga2O3/diamond interface.

Reduced thermal resistance of diamond-based ta-Ga2O3 MOSFET to 1.58 K mm/W.

Identified interfacial phonon modes as key to ultrahigh thermal conductance.

Abstract

The pursuit of extreme miniaturization and high power in 6G RF front-ends has cast thermal dissipation as the central challenge. Here, we have demonstrated the monolithic integration of functionally distinct single-crystal thin films, including \b{eta}-Ga2O3, Si, GaN, and LiTaO3, onto a single diamond substrate using a multi-step transfer printing technique. Focusing on the critical \b{eta}-Ga2O3/diamond interface, we achieve an exceptional interfacial thermal conductance (ITC) of 149 MW m-2 K-1 through ultra-high vacuum (UHV) annealing, creating an atomically sharp interface featuring covalent bonding. Vibrational electron energy-loss spectroscopy (EELS) analysis combining with molecular dynamics (MD) simulations reveal that distinctive interfacial phonon modes at the \b{eta}-Ga2O3/diamond heterointerface dominate ultrahigh ITC. We experimentally demonstrate that by improving the ITC, the thermal resistance (Rth) of a diamond-based \b{eta}-Ga2O3 MOSFET is driven to a record-low value of 1.58 K mm W-1, underscoring the critical role of interface engineering in near-junction thermal management for diamond-integrated devices. This work demonstrates a scalable, diamond-based monolithic integration platform designed to solve the near-junction thermal challenges in high-power RF front-ends.