Transfer of AlGaN/GaN RF-devices onto diamond substrates via van der Waals bonding

Gerrer, Thomas; Cimalla, V.; Waltereit, Patrick; Müller, Stefan; Benkhelifa, F.; Maier, Thomas; Czap, Heiko; Ambacher, O.; Quay, R.

doi:10.1017/s1759078718000582

Cited by 25 publications

(13 citation statements)

References 46 publications

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Section: Bonded Wafersmentioning

confidence: 99%

“…Van der Waals (VdW) bonding, a process first employed for GaAs thin films [121], has also been used to bond GaN devices and SCD/PCD substrates at temperatures below 300 • C [122,123]. This technique guarantees a good thermal interface (TBR GaN/SCD was estimated to be as low as 10 m 2 •K/GW [122]) without the observation of stress or degradation. RF-devices operating at 3 GHz with improved efficiency (PAE of 54.2% against 50.6% for GaN-on-Si HEMTs)) were demonstrated with SCD; on the other hand, the bonding obtained with PCD was not reproducible [123].…”

Section: Bonded Wafersmentioning

confidence: 99%

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Diamond/GaN HEMTs: Where from and Where to?

Mendes

Liehr²,

Li³

2022

Materials

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Gallium nitride is a wide bandgap semiconductor material with high electric field strength and electron mobility that translate in a tremendous potential for radio-frequency communications and renewable energy generation, amongst other areas. However, due to the particular architecture of GaN high electron mobility transistors, the relatively low thermal conductivity of the material induces the appearance of localized hotspots that degrade the devices performance and compromise their long term reliability. On the search of effective thermal management solutions, the integration of GaN and synthetic diamond with high thermal conductivity and electric breakdown strength shows a tremendous potential. A significant effort has been made in the past few years by both academic and industrial players in the search of a technological process that allows the integration of both materials and the fabrication of high performance and high reliability hybrid devices. Different approaches have been proposed, such as the development of diamond/GaN wafers for further device fabrication or the capping of passivated GaN devices with diamond films. This paper describes in detail the potential and technical challenges of each approach and presents and discusses their advantages and disadvantages.

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Section: Bonded Wafersmentioning

confidence: 99%

Section: Bonded Wafersmentioning

confidence: 99%

Diamond/GaN HEMTs: Where from and Where to?

Mendes

Liehr²,

Li³

2022

Materials

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“…Diamond has the highest known bulk thermal conductivity (>2000 W m –1 K –1 at room temperature). Several GaN/diamond integration methods have been pursued for improved thermal management: − overgrowth of a diamond heat spreader onto a device; GaN growth on a diamond substrate; and low-temperature bonding of diamond wafers to GaN . By far, the most successful integration method begins with the removal of the growth substrate, typically Si, and strain relief layers (SRLs), followed by polycrystalline diamond growth by microwave plasma chemical vapor deposition (MWCVD) onto the GaN backside. , It is imperative to minimize the thermal resistance between the GaN channel and diamond.…”

Section: Introductionmentioning

confidence: 99%

Crystalline Interlayers for Reducing the Effective Thermal Boundary Resistance in GaN-on-Diamond

Field

Cuenca

Smith

et al. 2020

ACS Appl. Mater. Interfaces

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Integrating diamond with GaN high electron mobility transistors (HEMTs) improves thermal management, ultimately increasing the reliability and performance of high-power high-frequency 2 RF amplifiers. Conventionally, an amorphous interlayer is used before growing polycrystalline diamond onto the GaN in these devices. This layer contributes significantly to the effective thermal boundary resistance (TBReff) between the GaN HEMT and the diamond, reducing the benefit of the diamond heat spreader. Replacing the amorphous interlayer with a higher thermal conductivity crystalline material would reduce TBReff and help to enable the full potential of GaN-on-diamond devices. In this work, a crystalline Al0.32Ga0.68N interlayer has been integrated into a GaN/AlGaN HEMT device epitaxy. Two samples were studied, one with diamond grown directly on the AlGaN interlayer and another incorporating a thin crystalline SiC layer between the AlGaN and diamond.The TBReff, measured using transient thermoreflectance, was improved for the sample with SiC (30 ± 5 m 2 K GW -1 ) compared to the sample without (107 ± 44 m 2 K GW -1 ). The reduced TBReff is thought to arise from improved adhesion between the SiC and the diamond compared to the diamond directly on the AlGaN due to an increased propensity for carbide bond formation between SiC and diamond. The stronger carbide bonds aid transmission of phonons across the interface, improving heat transport.

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“…However, heterogeneous integration of GaN with diamond leading to the GaN-on-diamond architecture is still challenging. Up to now, three kinds of approaches to fabricate the GaN-on-diamond architecture have been demonstrated: (i) diamond growth on GaN [13][14][15][16], (ii) GaN growth on diamond [17][18][19], and (iii) GaNdiamond bonding technology [20][21][22][23]. In the first two approaches, a nucleation layer is formed at the initial stage of growth, resulting in a large number of defects and grain boundaries at the interface, which have a negative impact on the thermal performance of the GaN-on-diamond device due to the poor thermal conductivity [5].…”

Section: Introductionmentioning

confidence: 99%

DFT-Based Studies on Carbon Adsorption on the wz-GaN Surfaces and the Influence of Point Defects on the Stability of the Diamond–GaN Interfaces

Sznajder

Hrytsak

2021

Materials

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Integration of diamond with GaN-based high-electron-mobility transistors improves thermal management, influencing the reliability, performance, and lifetime of GaN-based devices. The current GaN-on-diamond integration technology requires precise interface engineering and appropriate interfacial layers. In this respect, we performed first principles calculation on the stability of diamond–GaN interfaces in the framework of density functional theory. Initially, some stable adsorption sites of C atoms were found on the Ga- and N-terminated surfaces that enabled the creation of a flat carbon monolayer. Following this, a model of diamond–GaN heterojunction with the growth direction [111] was constructed based on carbon adsorption results on GaN{0001} surfaces. Finally, we demonstrate the ways of improving the energetic stability of diamond–GaN interfaces by means of certain reconstructions induced by substitutional dopants present in the topmost GaN substrate’s layer.

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Transfer of AlGaN/GaN RF-devices onto diamond substrates via van der Waals bonding

Cited by 25 publications

References 46 publications

Diamond/GaN HEMTs: Where from and Where to?

Diamond/GaN HEMTs: Where from and Where to?

Crystalline Interlayers for Reducing the Effective Thermal Boundary Resistance in GaN-on-Diamond

DFT-Based Studies on Carbon Adsorption on the wz-GaN Surfaces and the Influence of Point Defects on the Stability of the Diamond–GaN Interfaces

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