Analysis of Mechanical Strain in AlGaN/GaN HFETs

Yazdani, Hossein; Graff, Andreas; Simon-Najasek, Michél; Altmann, Frank; Brunner, F.; Ostermay, Ina; Chevtchenko, Serguei; Würfl, Joachim

doi:10.1002/pssa.202200683

Cited by 4 publications

(1 citation statement)

References 13 publications

(33 reference statements)

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“…However, previous work conducted on FBH devices have already established the influence of induced mechanical stress through passivation layers and/or gate metallization on GaN HFETs' characteristics, such as gate leakage and threshold voltage [9,10]. Earlier studies have demonstrated that mechanical stress induced during the fabrication process was transferred to the epitaxial layers beneath the gate region [11]. In the case of W1, the strained gate metal transfers compressive mechanical stress into the piezoelectric AlGaN/GaN epitaxial stack.…”

Section: Resultsmentioning

confidence: 99%

Low-resistive gate module for RF GaN-HFETs by electroplating

Yazdani,

Thies,

Stützle

et al. 2024

Semicond. Sci. Technol.

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This paper presents a novel approach for reducing the gate resistance (Rg) of K and Ka-band GaN HFETs with 150 nm gate length through a new gate metallization technique. The method involves increasing the gate cross-section via galvanic metallization using FBH's Ir-sputter gate technology, which allows an increase in gate metal thickness from the current 0.4 μm to approximately 1.0 μm for the transistors under investigation. This optimization leads to a substantial 50% reduction in gate series resistance, resulting in significant improvements in the RF performance. Specifically, the devices achieve 20% higher output power density and 10% better power-added efficiency (PAE) at 20 GHz and Vds = 20 V. The decreased gate resistance enables new degrees of freedom in design, such as longer gate fingers and/or shorter gate lengths, for more efficient power cells operating in this frequency range.

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Section: Resultsmentioning

confidence: 99%

Low-resistive gate module for RF GaN-HFETs by electroplating

Yazdani,

Thies,

Stützle

et al. 2024

Semicond. Sci. Technol.

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First-principles study on thermal transport properties of GaN under different cross-plane strain

Xue,

Li,

Fan

et al. 2024

International Journal of Heat and Mass Transfer

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Effect of temperature on the stability and performance of III-nitride HEMT magnetic field sensors

Shetty,

Kuchuk,

Zamani-Alavijeh

et al. 2024

Applied Physics Letters

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The study aimed to investigate the underlying physics limiting the temperature stability and performance of non-surface passivated Al0.34Ga0.66N/GaN Hall effect sensors, including contacts, under atmospheric conditions. The results obtained from analyzing the microstructural evolution in the Al0.34Ga0.66N/GaN Hall sensor heterostructure were found to correlate with the electrical performance of the Hall effect sensor. High-resolution x-ray photoelectron spectroscopy studies revealed the signature of surface oxidation in the GaN cap layer, as well as a slight out-diffusion of “Al” from the AlGaN barrier layer. To prevent the formation of a bumpy surface morphology at the Ohmic contact, we investigated the impact of “Pt” top Ohmic contacts. The application of a top “Pt” contact stack resulted in a smooth Ohmic contact surface and provided evidence that the bumpy surface morphology in Au-based Ohmic contacts is due to the formation of an Al-Au viscous alloy during rapid thermal annealing. In the early stages of thermal aging, the small drop in contact resistivity stabilized with subsequent thermal aging past the initial 550 h at 200 °C. The outcome is that the Al0.34Ga0.66N/GaN Hall effect sensors, even without surface passivation, exhibited a stable response to applied magnetic fields with no sign of significant degradation after 2800 h of thermal aging at 200 °C under atmospheric conditions. This observed stability in the Hall sensor without surface passivation can be attributed to a self-imposed surface oxidation of the cap layer during the early stages of aging, which serves as a protective layer for the device during subsequent extended periods of thermal aging at 200 °C.

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Analysis of Mechanical Strain in AlGaN/GaN HFETs

Cited by 4 publications

References 13 publications

Low-resistive gate module for RF GaN-HFETs by electroplating

Low-resistive gate module for RF GaN-HFETs by electroplating

First-principles study on thermal transport properties of GaN under different cross-plane strain

Effect of temperature on the stability and performance of III-nitride HEMT magnetic field sensors

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