Chemical Reactions Impede Thermal Transport Across Metal/β-Ga<sub>2</sub>O<sub>3</sub> Interfaces

Aller, Henry T.; Yu, Xiaoxiao; Wise, Adam; Howell, Robert S.; Gellman, Andrew J.; McGaughey, Alan J. H.; Malen, Jonathan A.

doi:10.1021/acs.nanolett.9b03017

Cited by 34 publications

(33 citation statements)

References 31 publications

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“…If the film were β-Ga 2 O 3 , this observation could be explained from a thermodynamic point of view as the Gibbs free energy for the reaction between Ti and β-Ga 2 O 3 is negative for most of the possible oxide forms of Ti, implying there is a driving force for β-Ga 2 O 3 reduction and Ti oxidation. The reduction of β-Ga 2 O 3 by less thermodynamically stable metal contacts has been reported previously [11][12][13]. In our case, we show that the same result is obtained with the metastable phase α-Ga 2 O 3 .…”

Section: Resultssupporting

confidence: 91%

Study of Ti contacts to corundum α-Ga₂O₃

Massabuau

Nicol

Adams

et al. 2021

J. Phys. D: Appl. Phys.

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We present a study of the electrical, structural and chemical properties of Ti contacts on atomic layer deposited α-Ga 2 O 3 film. Ti forms an ohmic contact with α-Ga 2 O 3 . The contact performance is highly dependent on the post-evaporation annealing temperature, where an improved conductivity is obtained when annealing at 450 • C, and a strong degradation when annealing at higher temperatures. Structural and chemical characterisation by transmission electron microscopy techniques reveal that the electrical improvement or degradation of the contact upon annealing can be attributed to oxidation of the Ti metallic layer by the Ga 2 O 3 film in combination with the possibility for Ti diffusion into the Au layer. The results highlight that the grain boundaries and inclusions in the Ga 2 O 3 film provide fast diffusion pathways for this reaction, leaving the α-Ga 2 O 3 crystallites relatively unaffected-this result differs from previous reports conducted on β-Ga 2 O 3 . This study underlines the necessity for a phase-specific and growth method-specific study of contacts on Ga 2 O 3 devices.

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Section: Resultssupporting

confidence: 91%

Study of Ti contacts to corundum α-Ga₂O₃

Massabuau

Nicol

Adams

et al. 2021

J. Phys. D: Appl. Phys.

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“…The TBC range from their measurements is consistent with our measurement of 81.7 MW/(m 2 K). In another study of the metal/β-Ga 2 O 3 interface by Aller et al, 10 the measured TBC at the Au/β-Ga 2 O 3 interface is about 45 MW/(m 2 K), which is higher than but similar to our measured value of 31.2 MW/(m 2 K).…”

Section: Resultssupporting

confidence: 86%

“…Another big difference is that the TBC values in ref 10 are generally higher than our measurements. In fact, the TBC values in ref 10 than our modeling results, and the reason would be further discussed in Section 3.5.…”

Section: Resultscontrasting

confidence: 86%

“…Chemical Reactions and the Defective Ga 2 O 3 Layer at Metal/β-Ga 2 O 3 Interfaces. As pointed out in a previous study of Ga 2 O 3 interfaces, 10 chemical reactions happen at the metal/β-Ga 2 O 3 interfaces considering the relatively high Gibbs free energy of β-Ga 2 O 3 . 32,33 The standard molar Gibbs free energies of formation Δ f G o at 298.15 K for different materials related to β-Ga 2 O 3 /metal contacts are shown in Table 3.…”

Section: Resultsmentioning

confidence: 75%

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Thermal Transport across Metal/β-Ga₂O₃ Interfaces

Shi

Yuan

Huang

et al. 2021

ACS Appl. Mater. Interfaces

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In this work, we study the thermal transport at β-Ga2O3/metal interfaces, which play important roles in heat dissipation and as electrical contacts in β-Ga2O3 devices. A theoretical Landauer approach was used to model and elucidate the factors that impact the thermal transport at these interfaces. Experimental measurements using time-domain thermoreflectance (TDTR) provided data for the thermal boundary conductance (TBC) between β-Ga2O3 and a range of metals used to create both Schottky and ohmic electrical contacts. From the modeling and experiments, the relation between the metal cutoff frequency and the corresponding TBC is observed. Moreover, the effect of the metal cutoff frequency on TBC is seen as the most significant factor followed by chemical reactions and defects between the metal and the β-Ga2O3. Among all β-Ga2O3/metal interfaces, for Schottky contacts, Ni/β-Ga2O3 interfaces show the highest TBC, while for ohmic contacts, Cr/β-Ga2O3 interfaces show the highest TBC. While there is a clear correlation between TBC and the phonon cutoff frequency of metal contacts, it is also important to control the chemical reactions and other defects at interfaces to maximize the TBC in this system.

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“…To extract the heat out of power electronic devices, high thermal conductivity substrates or top metal contacts with high thermal boundary conductance (TBC) near the gate are favorable. ,, However, direct growth of high-quality β-Ga 2 O 3 on high thermal conductivity substrates such as diamond and SiC is difficult because of the differences in crystal symmetry between β-Ga 2 O 3 and substrates . Recently, devices based on mechanically exfoliated monocrystalline β-Ga 2 O 3 nanomembranes have been fabricated and a record high drain current has been achieved via van der Waals bonding with a single-crystalline diamond. − These works demonstrated the great potential of β-Ga 2 O 3 devices.…”

Section: Introductionmentioning

confidence: 99%

Thermal Transport across Ion-Cut Monocrystalline β-Ga₂O₃ Thin Films and Bonded β-Ga₂O₃–SiC Interfaces

Cheng

You

et al. 2020

ACS Appl. Mater. Interfaces

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The ultrawide band gap, high breakdown electric field, and large-area affordable substrates make β-Ga 2 O 3 promising for applications of next-generation power electronics, while its thermal conductivity is at least 1 order of magnitude lower than other wide/ultrawide band gap semiconductors. To avoid the degradation of device performance and reliability induced by the localized Joule-heating, proper thermal management strategies are essential, especially for high-power high-frequency applications. This work reports a scalable thermal management strategy to heterogeneously integrate wafer-scale monocrystalline β-Ga 2 O 3 thin films on high thermal conductivity SiC substrates by the ion-cutting technique and room-temperature surface-activated bonding technique. The thermal boundary conductance (TBC) of the β-Ga 2 O 3 −SiC interfaces and thermal conductivity of the β-Ga 2 O 3 thin films were measured by time-domain thermoreflectance to evaluate the effects of interlayer thickness and thermal annealing. Materials characterizations were performed to understand the mechanisms of thermal transport in these structures. The results show that the β-Ga 2 O 3 −SiC TBC values are reasonably high and increase with decreasing interlayer thickness. The β-Ga 2 O 3 thermal conductivity increases more than twice after annealing at 800 °C because of the removal of implantation-induced strain in the films. A Callaway model is built to understand the measured thermal conductivity. Small spot-to-spot variations of both TBC and Ga 2 O 3 thermal conductivity confirm the uniformity and high quality of the bonding and exfoliation. Our work paves the way for thermal management of power electronics and provides a platform for β-Ga 2 O 3 -related semiconductor devices with excellent thermal dissipation.

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Chemical Reactions Impede Thermal Transport Across Metal/β-Ga₂O₃ Interfaces

Cited by 34 publications

References 31 publications

Study of Ti contacts to corundum α-Ga₂O₃

Study of Ti contacts to corundum α-Ga₂O₃

Thermal Transport across Metal/β-Ga₂O₃ Interfaces

Thermal Transport across Ion-Cut Monocrystalline β-Ga₂O₃ Thin Films and Bonded β-Ga₂O₃–SiC Interfaces

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Chemical Reactions Impede Thermal Transport Across Metal/β-Ga2O3 Interfaces

Cited by 34 publications

References 31 publications

Study of Ti contacts to corundum α-Ga2O3

Study of Ti contacts to corundum α-Ga2O3

Thermal Transport across Metal/β-Ga2O3 Interfaces

Thermal Transport across Ion-Cut Monocrystalline β-Ga2O3 Thin Films and Bonded β-Ga2O3–SiC Interfaces

Contact Info

Product

Resources

About

Chemical Reactions Impede Thermal Transport Across Metal/β-Ga₂O₃ Interfaces

Study of Ti contacts to corundum α-Ga₂O₃

Study of Ti contacts to corundum α-Ga₂O₃

Thermal Transport across Metal/β-Ga₂O₃ Interfaces

Thermal Transport across Ion-Cut Monocrystalline β-Ga₂O₃ Thin Films and Bonded β-Ga₂O₃–SiC Interfaces