Structure and properties of Ta/Al/Ta and Ti/Al/Ti/Au multilayer metal stacks formed as ohmic contacts on n-GaN

Boturchuk, Ievgen; Walter, Thomas; Julsgaard, Brian; Khatibi, Golta; Schwarz, Sabine; Stöger‐Pollach, Michael; Pedersen, Kjeld; Popok, Vladimír

doi:10.1007/s10854-019-02167-2

Cited by 5 publications

(3 citation statements)

References 24 publications

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“…Therefore, instead of using a single-layer Al or Ti contact, a composite Ti (contact layer)/Al (cap layer) ohmic contact can be deposited on the n + -GaN layer and annealed at 900 • C for 30 s to achieve very low-resistivity, stable, and high-performance ohmic contact [38]. Additionally, depositing a less resistive and less prone-to-oxidation gold (Au) layer on the Ti/Al layer significantly improves its performance [39]. To prevent high-energy Au atoms from penetrating through the Al layer at high temperatures, a nickel (Ni) barrier layer must be deposited between the Al and Au layers [38].…”

Section: Structures Design and Fabrication Possibilitiesmentioning

confidence: 99%

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Ghosh,

Deb,

Acharyya

et al. 2024

Nanomaterials

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In our pursuit of high-power terahertz (THz) wave generation, we propose innovative edge-terminated single-drift region (SDR) multi-quantum well (MQW) impact avalanche transit time (IMPATT) structures based on the AlxGa1−xN/GaN/AlxGa1−xN material system, with a fixed aluminum mole fraction of x = 0.3. Two distinct MQW diode configurations, namely p+-n junction-based and Schottky barrier diode structures, were investigated for their THz potential. To enhance reverse breakdown characteristics, we propose employing mesa etching and nitrogen ion implantation for edge termination, mitigating issues related to premature and soft breakdown. The THz performance is comprehensively evaluated through steady-state and high-frequency characterizations using a self-consistent quantum drift-diffusion (SCQDD) model. Our proposed Al0.3Ga0.7N/GaN/Al0.3Ga0.7N MQW diodes, as well as GaN-based single-drift region (SDR) and 3C-SiC/Si/3C-SiC MQW-based double-drift region (DDR) IMPATT diodes, are simulated. The Schottky barrier in the proposed diodes significantly reduces device series resistance, enhancing peak continuous wave power output to approximately 300 mW and DC to THz conversion efficiency to nearly 13% at 1.0 THz. Noise performance analysis reveals that MQW structures within the avalanche zone mitigate noise and improve overall performance. Benchmarking against state-of-the-art THz sources establishes the superiority of our proposed THz sources, highlighting their potential for advancing THz technology and its applications.

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Section: Structures Design and Fabrication Possibilitiesmentioning

confidence: 99%

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Ghosh,

Deb,

Acharyya

et al. 2024

Nanomaterials

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“…Consequently, high-quality ohmic contacts are helpful in achieving GaN-based HEMTs with high current densities, high extrinsic gain, and low Joule heating loss to allow high-temperature operation [228]. For conventional ohmic contacts by solid-phase reactions between the metal and (Al)GaN, Ta/Al/Ni/Au, Ti/Al/Ni/Au, Ti/Al/Ti/Au, Ti/Al/ Mo/Au, and Ti/Al/Pt/Au multiple metallisations are commonly used to fabricate low resistance Au-based ohmic contacts for AlGaN/GaN HEMTs [231][232][233][234][235]. However, Au acts as a deep-level contaminant with high diffusivity into the Si [236].…”

Section: Ohmic Contacts Technologymentioning

confidence: 99%

GaN-based power high-electron-mobility transistors on Si substrates: from materials to devices

Wu¹,

Xing²,

Li³

et al. 2023

Semicond. Sci. Technol.

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Conventional silicon (Si)-based power devices face physical limitations—such as switching speed and energy efficiency—which can make it difficult to meet the increasing demand for high-power, low-loss, and fast-switching-frequency power devices in power electronic converter systems. Gallium nitride (GaN) is an excellent candidate for next-generation power devices, capable of improving the conversion efficiency of power systems owing to its wide band gap, high mobility, and high electric breakdown field. Apart from their cost effectiveness, GaN-based power high-electron-mobility transistors (HEMTs) on Si substrates exhibit excellent properties—such as low ON-resistance and fast switching—and are used primarily in power electronic applications in the fields of consumer electronics, new energy vehicles, and rail transit, amongst others. During the past decade, GaN-on-Si power HEMTs have made major breakthroughs in the development of GaN-based materials and device fabrication. However, the fabrication of GaN-based HEMTs on Si substrates faces various problems—for example, large lattice and thermal mismatches, as well as ‘melt-back etching’ at high temperatures between GaN and Si, and buffer/surface trapping induced leakage current and current collapse. These problems can lead to difficulties in both material growth and device fabrication. In this review, we focused on the current status and progress of GaN-on-Si power HEMTs in terms of both materials and devices. For the materials, we discuss the epitaxial growth of both a complete multilayer HEMT structure, and each functional layer of a HEMT structure on a Si substrate. For the devices, breakthroughs in critical fabrication technology and the related performances of GaN-based power HEMTs are discussed, and the latest development in GaN-based HEMTs are summarised. Based on recent progress, we speculate on the prospects for further development of GaN-based power HEMTs on Si. This review provides a comprehensive understanding of GaN-based HEMTs on Si, aiming to highlight its development in the fields of microelectronics and integrated circuit technology.

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“…57 Various metal stack use different metal types and process schemes. [58][59][60][61] Other complex contact and field plate structures are also currently under intense investigation. 62 The gate metal stack is typically p-type GaN and Ni/Au.…”

Section: Fabrication Processmentioning

confidence: 99%

Current Trends in the Development of Normally-OFF GaN-on-Si Power Transistors and Power Modules: A Review

Kim

Zhang

et al. 2020

Journal of Elec Materi

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Gallium nitride (GaN) power transistors have attracted significant interest in the power electronics industry over the past decade as the next-generation power semiconductor devices. GaN power transistors are suitable for high power and high frequency applications due to their higher electron mobility, temperature tolerance, electrical conductivity, critical breakdown electric field, and breakdown voltage compared to the conventional silicon-based transistors and other wide bandgap (WBG) power transistors. In particular, GaN-on-silicon (GaN-on-Si) technology has opened up the possibility of manufacturing high-performance, low-cost WBG power devices in silicon-compatible fabrication facilities. The first GaN power transistor structure to be developed was the normally-ON depletion mode (D-mode) device. It relies on the highly mobile two-dimension electron gas (2DEG) at the GaN/AlGaN epitaxial layers' interface to provide very low on-resistance. The normally-OFF enhancement mode (E-mode) GaN power transistor soon became available by controlling the 2DEG using various gate structures. This paper provides a review of the developments of GaN power transistors followed by a survey on current state-of-the-art GaN power technologies and applications, including comparisons between GaN growth substrates and developments of enhancement mode (E-mode) device structures and their process techniques. Moreover, developments of power module designs are also addressed, including gate driver designs and their requirements, and packaging techniques for power transistors and power modules.

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Structure and properties of Ta/Al/Ta and Ti/Al/Ti/Au multilayer metal stacks formed as ohmic contacts on n-GaN

Cited by 5 publications

References 24 publications

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

GaN-based power high-electron-mobility transistors on Si substrates: from materials to devices

Current Trends in the Development of Normally-OFF GaN-on-Si Power Transistors and Power Modules: A Review

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