Significantly reduced thermal conductivity in <b>
                     <i>β</i>
                  </b>-(Al0.1Ga0.9)2O3/Ga2O3 superlattices

Cheng, Zhe; Tanen, Nicholas; Chang, Celesta S.; Shi, Jingjing; McCandless, Jonathan P.; Muller, David A.; Jena, Debdeep; Xing, Huili Grace; Graham, Samuel

doi:10.1063/1.5108757

Cited by 25 publications

(11 citation statements)

References 33 publications

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“…Temperature-dependent thermal conductivity measurements were performed on β-Ga 2 O 3 (521 nm) and β-(Al 0.27 Ga 0.73 ) 2 O 3 (505 nm) films with a similar thickness using TDTR from room temperature up to 600 °C (Figure ). As the temperature increases, the thermal conductivity of the β-Ga 2 O 3 film monotonically decreases due to the increased Umklapp scattering rate; the temperature-dependent thermal conductivity of bulk β-Ga 2 O 3 shows a similar trend and has been reported in the literature . In contrast, the thermal conductivity of the β-(Al 0.27 Ga 0.73 ) 2 O 3 film is relatively invariant across this temperature range.…”

Section: Resultssupporting

confidence: 86%

Thermal Conductivity of β-Phase Ga₂O₃ and (Al_xGa_1–_x)₂O₃ Heteroepitaxial Thin Films

Song

Ranga

Zhang

et al. 2021

ACS Appl. Mater. Interfaces

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Heteroepitaxy of β-phase gallium oxide (β-Ga 2 O 3 ) thin films on foreign substrates shows promise for the development of next-generation deep ultraviolet solar blind photodetectors and power electronic devices. In this work, the influences of the film thickness and crystallinity on the thermal conductivity of (2̅ 01)-oriented β-Ga 2 O 3 heteroepitaxial thin films were investigated. Unintentionally doped β-Ga 2 O 3 thin films were grown on c-plane sapphire substrates with off-axis angles of 0°and 6°toward ⟨112̅ 0⟩ via metal−organic vapor phase epitaxy (MOVPE) and low-pressure chemical vapor deposition. The surface morphology and crystal quality of the β-Ga 2 O 3 thin films were characterized using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The thermal conductivities of the β-Ga 2 O 3 films were measured via time-domain thermoreflectance. The interface quality was studied using scanning transmission electron microscopy. The measured thermal conductivities of the submicron-thick β-Ga 2 O 3 thin films were relatively low as compared to the intrinsic bulk value. The measured thin film thermal conductivities were compared with the Debye−Callaway model incorporating phononic parameters derived from first-principles calculations. The comparison suggests that the reduction in the thin film thermal conductivity can be partially attributed to the enhanced phonon-boundary scattering when the film thickness decreases. They were found to be a strong function of not only the layer thickness but also the film quality, resulting from growth on substrates with different offcut angles. Growth of β-Ga 2 O 3 films on 6°offcut sapphire substrates was found to result in higher crystallinity and thermal conductivity than films grown on on-axis c-plane sapphire. However, the β-Ga 2 O 3 films grown on 6°offcut sapphire exhibit a lower thermal boundary conductance at the β-Ga 2 O 3 / sapphire heterointerface. In addition, the thermal conductivity of MOVPE-grown (2̅ 01)-oriented β-(Al x Ga 1−x ) 2 O 3 thin films with Al compositions ranging from 2% to 43% was characterized. Because of phonon-alloy disorder scattering, the β-(Al x Ga 1−x ) 2 O 3 films exhibit lower thermal conductivities (2.8−4.7 W/m•K) than the β-Ga 2 O 3 thin films. The dominance of the alloy disorder scattering in β-(Al x Ga 1−x ) 2 O 3 is further evidenced by the weak temperature dependence of the thermal conductivity. This work provides fundamental insight into the physical interactions that govern phonon transport within heteroepitaxially grown β-phase Ga 2 O 3 and (Al x Ga 1−x ) 2 O 3 thin films and lays the groundwork for the thermal modeling and design of β-Ga 2 O 3 electronic and optoelectronic devices.

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Section: Resultssupporting

confidence: 86%

Thermal Conductivity of β-Phase Ga₂O₃ and (Al_xGa_1–_x)₂O₃ Heteroepitaxial Thin Films

Song

Ranga

Zhang

et al. 2021

ACS Appl. Mater. Interfaces

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“…5,14,16 6 1, the measured thermal conductivity of Samp1 is 1.76 W/m-K, which is much lower than that of bulk -Ga2O3 (10-30 W/m-K). 4 To understand this low thermal conductivity value, TEM was used to study the fine structure, as shown in Fig. 1 The measured thermal conductivity of Samp2-4 is about 1.5 W/m-K, which is much lower than the bulk counterpart and slightly lower than that of Samp1.…”

Section: Samples and Methodsmentioning

confidence: 99%

“…1 However, the thermal conductivity of bulk β-Ga2O3 (10-30 W/m-K, depending on crystal orientations) is at least one order of magnitude lower than those of other wide bandgap semiconductors such as GaN (230 W/m-K), 4H-SiC (490 W/m-K), AlN (320 W/m-K), and diamond (>2000 W/m-K). [2][3][4] Size effects, doping, and alloying can further reduce the thermal conductivity of Ga2O3-based materials which is an essential thermophysical property that impacts device behavior and reliability. 4 As seen in other wide bandgap devices, higher device operating temperatures (as a result of the low thermal conductivity in β-Ga2O3) will result in faster device degradation and shorter lifetimes.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4] Size effects, doping, and alloying can further reduce the thermal conductivity of Ga2O3-based materials which is an essential thermophysical property that impacts device behavior and reliability. 4 As seen in other wide bandgap devices, higher device operating temperatures (as a result of the low thermal conductivity in β-Ga2O3) will result in faster device degradation and shorter lifetimes. Therefore, efficient thermal dissipation while minimizing device junction temperature is one of the main challenges for β-Ga2O3 -based devices, especially for high power and high frequency devices where localized Joule-heating results in hot-spots that can lead to degradation and failure.…”

Section: Introductionmentioning

confidence: 99%

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Integration of polycrystalline Ga2O3 on diamond for thermal management

Cheng

Wheeler

Bai

et al. 2020

Applied Physics Letters

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Gallium oxide (Ga2O3) has attracted great attention for electronic device applications due to its ultra-wide bandgap, high breakdown electric field, and large-area affordable substrates grown from the melt. However, its thermal conductivity is significantly lower than that of other wide bandgap semiconductors such as SiC, AlN, and GaN, which will impact its ability to be used in high power density applications. Thermal management in Ga2O3 electronics will be the key for device reliability, especially for high power and high frequency devices. Similar to the method of cooling GaN-based high electron mobility transistors by integrating it with high thermal conductivity diamond substrates, this work studies the possibility of heterogeneous integration of Ga2O3 with diamond for thermal management of Ga2O3 devices. In this work, Ga2O3 was deposited onto single crystal diamond substrates by atomic layer deposition (ALD) and the thermal properties of ALD-Ga2O3 thin films and Ga2O3-diamond interfaces with different interface pretreatments were measured by Time-domain Thermoreflectance (TDTR). We observed very low thermal conductivity of these Ga2O3 thin films (about 1.5 W/m-K) due to the extensive phonon grain boundary scattering resulting from the nanocrystalline nature of the Ga2O3 film. However, the measured thermal boundary conductance (TBC) of the Ga2O3diamond interfaces are about 10 times larger than that of the Van der Waals bonded Ga2O3diamond interfaces, which indicates the significant impact of interface bonding on TBC.Furthermore, the TBC of the Ga-rich and O-rich Ga2O3-diamond interfaces are about 20% smaller than that of the clean interface, indicating interface chemistry affects interfacial thermal transport. Overall, this study shows that a high TBC can be obtained from strong interfacial bonds across Ga2O3-diamond interfaces, providing a promising route to improving the heat dissipation from Ga2O3 devices with lateral architectures.

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“…[263] Formation of superlattices using gallium oxide can be looked into. [264][265] These may even be utilized for the bandgap engineering. 2D Van-der Waals heterostructures can be fabricated with the help of mechanically exfoliated Ga 2 O 3 flakes.…”

Section: Novel Effectsmentioning

confidence: 99%

A Strategic Review on Gallium Oxide Based Deep‐Ultraviolet Photodetectors: Recent Progress and Future Prospects

Kaur

Kumar

2021

Advanced Optical Materials

305

153

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With the use of UV‐C radiation sterilizers on the rise in the wake of the recent pandemic, it has become imperative to have health safety systems in place to curb the ill‐effects on humans. This requires detection systems with suitable spectral response to the “invisible to the naked eye” radiation leaks with utmost sensitivity and swiftness. State of the art deep‐UV photodetectors based on the wide bandgap material gallium oxide have achieved responsivities up to few hundred A W−1 while the minimum response time achieved is few hundred nanoseconds. However, due to the trade‐off between these two key parameters, the ultimate performance of the photodetectors remains inadequate. The focus here is to give a thorough review of the gallium oxide based photodetectors, their recent progress and future prospects. This review highlights the fundamental physics and the key parameters such as dark current, responsivity, and response time with their dependence on the material properties. Exploration of the reasons behind current scenario in the field of gallium oxide is comprehensively and critically analyzed. The key challenges which limit device performance and inhibit the realization of real‐world practical detectors are also described. The lacunae currently plaguing the field is also discussed with possible remedial solutions.

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Significantly reduced thermal conductivity in β -(Al0.1Ga0.9)2O3/Ga2O3 superlattices

Cited by 25 publications

References 33 publications

Thermal Conductivity of β-Phase Ga₂O₃ and (Al_xGa_1–_x)₂O₃ Heteroepitaxial Thin Films

Thermal Conductivity of β-Phase Ga₂O₃ and (Al_xGa_1–_x)₂O₃ Heteroepitaxial Thin Films

Integration of polycrystalline Ga2O3 on diamond for thermal management

A Strategic Review on Gallium Oxide Based Deep‐Ultraviolet Photodetectors: Recent Progress and Future Prospects

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Significantly reduced thermal conductivity in β -(Al0.1Ga0.9)2O3/Ga2O3 superlattices

Cited by 25 publications

References 33 publications

Thermal Conductivity of β-Phase Ga2O3 and (AlxGa1–x)2O3 Heteroepitaxial Thin Films

Thermal Conductivity of β-Phase Ga2O3 and (AlxGa1–x)2O3 Heteroepitaxial Thin Films

Integration of polycrystalline Ga2O3 on diamond for thermal management

A Strategic Review on Gallium Oxide Based Deep‐Ultraviolet Photodetectors: Recent Progress and Future Prospects

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Product

Resources

About

Thermal Conductivity of β-Phase Ga₂O₃ and (Al_xGa_1–_x)₂O₃ Heteroepitaxial Thin Films

Thermal Conductivity of β-Phase Ga₂O₃ and (Al_xGa_1–_x)₂O₃ Heteroepitaxial Thin Films