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Authors = Joff Derluyn

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6 pages, 3076 KiB  
Article
Low Buffer Trapping Effects above 1200 V in Normally off GaN-on-Silicon Field Effect Transistors
by Idriss Abid, Youssef Hamdaoui, Jash Mehta, Joff Derluyn and Farid Medjdoub
Micromachines 2022, 13(9), 1519; https://doi.org/10.3390/mi13091519 - 14 Sep 2022
Cited by 2 | Viewed by 2498
Abstract
We report on the fabrication and electrical characterization of AlGaN/GaN normally off transistors on silicon designed for high-voltage operation. The normally off configuration was achieved with a p-gallium nitride (p-GaN) cap layer below the gate, enabling a positive threshold voltage higher than +1 [...] Read more.
We report on the fabrication and electrical characterization of AlGaN/GaN normally off transistors on silicon designed for high-voltage operation. The normally off configuration was achieved with a p-gallium nitride (p-GaN) cap layer below the gate, enabling a positive threshold voltage higher than +1 V. The buffer structure was based on AlN/GaN superlattices (SLs), delivering a vertical breakdown voltage close to 1.5 kV with a low leakage current all the way to 1200 V. With the grounded substrate, the hard breakdown voltage transistors at VGS = 0 V is 1.45 kV, corresponding to an outstanding average vertical breakdown field higher than 2.4 MV/cm. High-voltage characterizations revealed a state-of-the-art combination of breakdown voltage at VGS = 0 V together with low buffer electron trapping effects up to 1.4 kV, as assessed by means of substrate ramp measurements. Full article
(This article belongs to the Special Issue III–V Compound Semiconductors and Devices)
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9 pages, 3800 KiB  
Article
AlGaN Channel High Electron Mobility Transistors with Regrown Ohmic Contacts
by Idriss Abid, Jash Mehta, Yvon Cordier, Joff Derluyn, Stefan Degroote, Hideto Miyake and Farid Medjdoub
Electronics 2021, 10(6), 635; https://doi.org/10.3390/electronics10060635 - 10 Mar 2021
Cited by 40 | Viewed by 7105
Abstract
High power electronics using wide bandgap materials are maturing rapidly, and significant market growth is expected in a near future. Ultra wide bandgap materials, which have an even larger bandgap than GaN (3.4 eV), represent an attractive choice of materials to further push [...] Read more.
High power electronics using wide bandgap materials are maturing rapidly, and significant market growth is expected in a near future. Ultra wide bandgap materials, which have an even larger bandgap than GaN (3.4 eV), represent an attractive choice of materials to further push the performance limits of power devices. In this work, we report on the fabrication of AlN/AlGaN/AlN high-electron mobility transistors (HEMTs) using 50% Al-content on the AlGaN channel, which has a much wider bandgap than the commonly used GaN channel. The structure was grown by metalorganic chemical vapor deposition (MOCVD) on AlN/sapphire templates. A buffer breakdown field as high as 5.5 MV/cm was reported for short contact distances. Furthermore, transistors have been successfully fabricated on this heterostructure, with low leakage current and low on-resistance. A remarkable three-terminal breakdown voltage above 4 kV with an off-state leakage current below 1 μA/mm was achieved. A regrown ohmic contact was used to reduce the source/drain ohmic contact resistance, yielding a drain current density of about 0.1 A/mm. Full article
(This article belongs to the Special Issue Advances in Ultra-Wide Bandgap Devices)
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12 pages, 8863 KiB  
Article
High Breakdown Voltage and Low Buffer Trapping in Superlattice GaN-on-Silicon Heterostructures for High Voltage Applications
by Alaleh Tajalli, Matteo Meneghini, Sven Besendörfer, Riad Kabouche, Idriss Abid, Roland Püsche, Joff Derluyn, Stefan Degroote, Marianne Germain, Elke Meissner, Enrico Zanoni, Farid Medjdoub and Gaudenzio Meneghesso
Materials 2020, 13(19), 4271; https://doi.org/10.3390/ma13194271 - 25 Sep 2020
Cited by 17 | Viewed by 4117
Abstract
The aim of this work is to demonstrate high breakdown voltage and low buffer trapping in superlattice GaN-on-Silicon heterostructures for high voltage applications. To this aim, we compared two structures, one based on a step-graded (SG) buffer (reference structure), and another based on [...] Read more.
The aim of this work is to demonstrate high breakdown voltage and low buffer trapping in superlattice GaN-on-Silicon heterostructures for high voltage applications. To this aim, we compared two structures, one based on a step-graded (SG) buffer (reference structure), and another based on a superlattice (SL). In particular, we show that: (i) the use of an SL allows us to push the vertical breakdown voltage above 1500 V on a 5 µm stack, with a simultaneous decrease in vertical leakage current, as compared to the reference GaN-based epi-structure using a thicker buffer thickness. This is ascribed to the better strain relaxation, as confirmed by X-Ray Diffraction data, and to a lower clustering of dislocations, as confirmed by Defect Selective Etching and Cathodoluminescence mappings. (ii) SL-based samples have significantly lower buffer trapping, as confirmed by substrate ramp measurements. (iii) Backgating transient analysis indicated that traps are located below the two-dimensional electron gas, and are related to CN defects. (iv) The signature of these traps is significantly reduced on devices with SL. This can be explained by the lower vertical leakage (filling of acceptors via electron injection) or by the slightly lower incorporation of C in the SL buffer, due to the slower growth process. SL-based buffers therefore represent a viable solution for the fabrication of high voltage GaN transistors on silicon substrate, and for the simultaneous reduction of trapping processes. Full article
(This article belongs to the Section Electronic Materials)
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9 pages, 3035 KiB  
Article
Vertical Leakage in GaN-on-Si Stacks Investigated by a Buffer Decomposition Experiment
by Alaleh Tajalli, Matteo Borga, Matteo Meneghini, Carlo De Santi, Davide Benazzi, Sven Besendörfer, Roland Püsche, Joff Derluyn, Stefan Degroote, Marianne Germain, Riad Kabouche, Idriss Abid, Elke Meissner, Enrico Zanoni, Farid Medjdoub and Gaudenzio Meneghesso
Micromachines 2020, 11(1), 101; https://doi.org/10.3390/mi11010101 - 17 Jan 2020
Cited by 4 | Viewed by 6979
Abstract
We investigated the origin of vertical leakage and breakdown in GaN-on-Si epitaxial structures. In order to understand the role of the nucleation layer, AlGaN buffer, and C-doped GaN, we designed a sequential growth experiment. Specifically, we analyzed three different structures grown on silicon [...] Read more.
We investigated the origin of vertical leakage and breakdown in GaN-on-Si epitaxial structures. In order to understand the role of the nucleation layer, AlGaN buffer, and C-doped GaN, we designed a sequential growth experiment. Specifically, we analyzed three different structures grown on silicon substrates: AlN/Si, AlGaN/AlN/Si, C:GaN/AlGaN/AlN/Si. The results demonstrate that: (i) the AlN layer grown on silicon has a breakdown field of 3.25 MV/cm, which further decreases with temperature. This value is much lower than that of highly-crystalline AlN, and the difference can be ascribed to the high density of vertical leakage paths like V-pits or threading dislocations. (ii) the AlN/Si structures show negative charge trapping, due to the injection of electrons from silicon to deep traps in AlN. (iii) adding AlGaN on top of AlN significantly reduces the defect density, thus resulting in a more uniform sample-to-sample leakage. (iv) a substantial increase in breakdown voltage is obtained only in the C:GaN/AlGaN/AlN/Si structure, that allows it to reach VBD > 800 V. (v) remarkably, during a vertical I–V sweep, the C:GaN/AlGaN/AlN/Si stack shows evidence for positive charge trapping. Holes from C:GaN are trapped at the GaN/AlGaN interface, thus bringing a positive charge storage in the buffer. For the first time, the results summarized in this paper clarify the contribution of each buffer layer to vertical leakage and breakdown. Full article
(This article belongs to the Special Issue Wide Bandgap Based Devices: Design, Fabrication and Applications)
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