Thermal conductance across β-Ga2O3-diamond van der Waals heterogeneous interfaces

Abstract

Because of its ultra-wide bandgap, high breakdown electric field, and large-area affordable substrates grown from the melt, β-Ga2O3 has attracted great attention recently for potential applications of power electronics. However, its thermal conductivity is significantly lower than those of other wide bandgap semiconductors, such as AlN, SiC, GaN, and diamond. To ensure reliable operation with minimal self-heating at high power, proper thermal management is even more essential for Ga2O3 devices. Similarly to the past approaches aiming to alleviate selfheating in GaN high electron mobility transistors (HEMTs), a possible solution has been to integrate thin Ga2O3 membranes with diamond to fabricate Ga2O3-on-diamond lateral metalsemiconductor field-effect transistor (MESFET) or metal-oxide-semiconductor field-effect transistor (MOSFET) devices by taking advantage of the ultra-high thermal conductivity of diamond. Even though the thermal boundary conductance (TBC) between wide bandgap semiconductor devices such as GaN HEMTs and a diamond substrate is of primary importance for heat dissipation in these devices, fundamental understanding of the Ga2O3/diamond thermal interface is still missing. In this work, we study the thermal transport across the interfaces of Ga2O3 exfoliated onto a single crystal diamond. The Van der Waals bonded Ga2O3-diamond TBC is measured to be 17 -1.7/+2.0 MW/m 2 -K, which is comparable to the TBC of several physical-vapor-deposited metals on diamond. A Landauer approach is used to help understand phonon transport across perfect Ga2O3-diamond interface, which in turn sheds light on the possible TBC one could achieve with an optimized interface. A reduced thermal conductivity of the Ga2O3 nano-membrane is also observed due to additional phonon-membrane boundary scattering. The impact of the Ga2O3-substrate TBC and substrate thermal conductivity on the thermal performance of a power device are modeled and discussed. Without loss of generality, this study is not only important for Ga2O3 power electronics applications which would not be realistic without a thermal management solution, but also for the fundamental thermal science of heat transport across Van der Waals bonded interfaces.

Interfacial Thermal Conductance across Room-Temperature-Bonded GaN/Diamond Interfaces for GaN-on-Diamond Devices

“…More details about TDTR measurements on similar sample structures can be found in the literature. 10,26,28,29 An example of the agreement between experimental data (Exp) and the analytical heat transfer solution (Theo) in TDTR data fitting is shown in Figure 1 HPHT sample as expected and matches well with literature values of high-purity diamonds. 30,31 The measured thermal conductivity of the GaN layer (~1.88 μm) in Samp2 is close to experimentally measured bulk values and lower than density-function-theory calculated (DFT) values because of impurities in these samples.…”

Integration of polycrystalline Ga2O3 on diamond for thermal management

“…The substrates were stored in ethanol and were dried in N2 immediately prior to transfer into the Ga2O3 growth reactor. Thin films (~30-115 nm) were deposited on single crystal (100) diamond substrates in a Fiji 200 G2 reactor at 350°C using alternating cycles of trimethylgallium (TMG, STREM PURATREM) as 5 the Ga precursor and a remote pure oxygen plasma as the oxidizing source. All samples utilized a turbo pump to drop the pressure in the chamber to 8 mTorr during plasma exposure.…”

Experimental observation of high intrinsic thermal conductivity of AlN

“…The local Al thickness is determined by the picosecond acoustic technique. 27 [29][30][31] The TDTR sensitivity and data fitting can be found in the Supplementary Information. We used a Monte Carlo method to calculate the errors of these TDTR measurements and more details is included in the Supplementary Information.…”