Thermal Boundary Resistance in GaN Films Measured by Time Domain Thermoreflectance with Robust Monte Carlo Uncertainty Estimation

Bougher, Thomas L.; Yates, Luke; Lo, Chien-Fong; Johnson, Wayne; Graham, Samuel; Cola, Baratunde A.

doi:10.1080/15567265.2016.1154630

Cited by 77 publications

(50 citation statements)

References 27 publications

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“…The error bars of TDTR measurements is estimated by a Monte Carlo method. 28 The Ga2O3diamond TBC is in the TBC range of the transferred metal films on silicon, SiO2, and sapphire substrates and is comparable to the TBC of physical-vapor-deposited metals on diamond. The Ga2O3-diamond TBC is mainly affected by three factors: the weak Van der Waals force between Ga2O3 and diamond, the small contact area at the interface, and the large phonon density of states (DOS) mismatch between Ga2O3 and diamond.…”

Section: Resultsmentioning

confidence: 86%

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

et al. 2019

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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.

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Section: Resultsmentioning

confidence: 86%

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

et al. 2019

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“…4 For this technically important interface, a number of experimental and simulation studies have been reported to understand thermal transport across the GaN-SiC interfaces. [4][5][6][7][8][9][10][11][12] The calculated TBC of GaN-SiC interface is close to 500 MW/m 2 -K by molecular dynamics (MD) simulations, twice as the experimentally measured GaN-SiC TBC. [4][5][6][7][8][9] Only a firstprinciple calculation matches with experimental values, 12 but acoustic mismatch model (AMM) and diffusive mismatch model (DMM) are used to calculate transmission in their work, which did not include the contribution of inelastic scatterings and cannot address the problem of local nonequilibrium phonon transport near the interface.…”

Section: Introductionmentioning

confidence: 71%

High Thermal Boundary Conductance across Bonded Heterogeneous GaN–SiC Interfaces

Cheng²,

Shi³

et al. 2019

ACS Appl. Mater. Interfaces

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GaN-based high electron mobility transistors have the potential to be widely used in high-power and high-frequency electronics while their maximum output powers are limited by high channel temperature induced by near-junction Joule-heating, which degrades device performance and reliability. Increasing the thermal boundary conductance (TBC) between GaN and SiC will aid in the heat dissipation of GaN-on-SiC power devices, taking advantage of the high thermal conductivity of the SiC substrate. However, a good understanding of the TBC of this technically important interface is still lacking due to the complicated nature of interfacial heat transport. With the AlN being the typical interfacial layer between GaN and SiC, there are issues concerning the quality of the AlN as well as the defects that are contained in the GaN near this growth interface which can impede heat flow. In this work, a lattice-mismatch-insensitive surface activated bonding method is used to bond GaN directly to SiC and thus eliminating the AlN layer altogether. This allows for the direct integration of high quality GaN layers with SiC to create a high thermal boundary conductance interface. Time-domain thermoreflectance (TDTR) is used to measure the thermal properties of the GaN thermal conductivity and GaN-SiC TBC. The measured GaN thermal conductivity is larger than that of GaN grown by molecular-beam epitaxy (MBE) on SiC,showing the impact of reducing the dislocations in the GaN near the interface. High GaN-SiC TBC is observed for the bonded GaN-SiC interfaces, especially for the annealed interface whose TBC (230 MW/m 2 -K) is close to the highest values ever reported. Thus, this method provides the benefit of both a high TBC with higher GaN thermal conductivity near the interface to aid in heat dissipation. To understand the structure-thermal property relation, STEM and EELS are used to characterize the interface structure. The results show that, for the as-bonded sample, there exists an amorphous layer near the interface for the as bonded samples. This amorphous layer is crystallized upon annealing, leading to the high TBC found in our work. Our work not only paves the way for thermal transport across bonded interfaces where bonding and local chemistry are tunable, which will enable and stimulate future study of new theory of interfacial thermal transport mechanism, but also impact real-world applications of semiconductor integration and packaging where thermal dissipation always plays an important role.

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“…Ti/G/SiO 2 , Ti/h‐BN/SiO 2 , and Ti/h‐BN/G/SiO 2 values measured using TDTR. Error bars were calculated using an MC method . G/SiO 2 and h‐BN/SiO 2 data taken from previous studies, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Error bars were calculated using an MC method. [49] G/SiO 2 and h-BN/SiO 2 data taken from previous studies, [88,89] respectively. Ti/G, Ti/h-BN, and h-BN/G TBC values estimated using series resistance approximation.…”

Section: Resultsmentioning

confidence: 99%

“…The experimental data were fit to a thermal model to extract the thermal properties of interest. In the two‐color TDTR setup used in this study, described previously, the output of a Spectra Physics Ti:Sapphire ( λ = 800 nm, 40 nJ pulse −1 ) laser with ≈150 fs pulse width and a repetition rate of ≈80 MHz was split into two beam paths (pump and probe) where the pump beam was modulated at a frequency of 8.8 MHz, then frequency doubled using a BiBO crystal. The pump and probe struck the surface concentrically at a normal angle of incidence and were focused to 1/ e 2 radii of ≈5 and ≈3 μm, respectively, using pump and probe powers of 10 and 4 mW, respectively.…”

Section: Methodsmentioning

confidence: 99%

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Thermal Boundary Conductance and Phonon Transmission in Hexagonal Boron Nitride/Graphene Heterostructures

Brown

Bougher

Zhang

et al. 2019

Physica Status Solidi (a)

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Two‐dimensional (2D) materials such as graphene and hexagonal boron nitride (h‐BN) have attracted interest as a conductor/insulator pair in next‐generation devices because of their unique physical properties; however, the thermal transport at the interfaces must be understood to accurately predict the performance of heterostructures composed of these materials. Time‐domain thermoreflectance (TDTR) is used to estimate the thermal boundary conductance (TBC) at the interface of h‐BN and graphene to be 34.5 (+11.6/−7.4) MW m−2 K−1. The advantage of TDTR is that it does not need to create a large temperature gradient at the interface of heterostructures, but it has not yet been used for h‐BN/graphene interface. Phonon transmission and TBC at the h‐BN/graphene interface are predicted by two different formulations of the diffuse mismatch model (DMM) for anisotropic materials. The analysis of phonon transmission and temperature dependence of TBC establishes the flexural branch in the ab‐plane, and the c‐plane longitudinal acoustic branch of graphene and h‐BN are the dominant contributors when implementing both the DMM models. The methodology developed herein can be used to analyze heterostructures of other 2D materials.

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Thermal Boundary Resistance in GaN Films Measured by Time Domain Thermoreflectance with Robust Monte Carlo Uncertainty Estimation

Cited by 77 publications

References 27 publications

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

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

High Thermal Boundary Conductance across Bonded Heterogeneous GaN–SiC Interfaces

Thermal Boundary Conductance and Phonon Transmission in Hexagonal Boron Nitride/Graphene Heterostructures

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