Student Presentation
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May 11, 2022 // 4:50pm
11.2 Design and Manufacture of Edge Termination in Vertical GaN Diodes: Electric Field Distribution Probed by Second Harmonic Generation
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12.1.2023 Thermal management in GaN-devices for increased power density
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12.3.2023 Characterization of a Novel Thermal Interface Material based on Nanoparticles for High Power Device Package Assembly
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15.2.2023 Selective Area Growth of B-Ga2O3
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10.1.3.2024 3D Diamond Growth for GaN Cooling and TBR Reduction
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10.1.4.2024 Thermal Dissipation Enhancement Using a Metal-Diamond Composite Heat Spreaders in High-Power RF MMICs
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11.2.2.2024 Mapping of Local Threshold Voltage in AlGaN/GaN HEMTs
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11.2.3.2024 Time-Dependent Conduction Mechanisms in Superlattice Layers on 200 mm Engineered Substrates
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3A.2 – Normally-Off N-Polar GaN/AlN Transistors with p-NiO Gate Stacks
Abstract
Normally-off high-electron-mobility transistors with p-type NiO gate on an N-polar GaN/AlN material platform are demonstrated. A direct comparison with p-NiO gated HEMTs, Metal-Oxide-Semiconductor (MOS)-gated HEMTs and AlN trench MOSFET devices on the same wafer shows the utility of the NiO in shifting the threshold voltage to positive values. HEMTs with a p-NiO gate exhibit a positive threshold voltage of 1.24 V with a high ON/OFF drain current ratio of 107, a yield as high as 70% is achieved. Breakdown voltages of over 3000 V in co-fabricated AlN trench structures highlight the strong potential of the N-polar GaN/AlN platform for power electronic devices. The potential of this technology for future commercialization/manufacturing is demonstrated. -
7A.3 – Heteroepitaxial Growth of α-Ga2O3 by MOCVD on a, m, r and c-Plane Sapphire
Abstract
With a wide bandgap of 5.4 eV, α-Ga2O3 is a promising material for high-breakdown power devices and solar-blind photodetectors but is difficult to grow due its metastability. Sapphire, being isostructural to α-Ga2O3, is therefore the substrate of choice to stabilise epitaxial layers of α-Ga2O3. Since each sapphire plane imposes different surface energy and strain conditions on the epitaxial layer, the choice of substrate orientation is critical to the stabilisation of α-phase. In this work, Ga2O3 thin films were deposited simultaneously on (11-20), a-plane, (10-10) m-plane, (0001) c-plane, and (01-12) r-plane sapphire substrates using metal-organic chemical vapour deposition (MOCVD), and XRD analysis was performed to confirm the resultant phase of Ga2O3 on each plane. We found that, under the same conditions, Ga2O3 assumed β phase on c-plane, mixed phase α & β on a-plane and r-plane, and pure α phase on m-plane. These results indicate that m-plane is most conducive to growing phase-pure α-Ga2O3 layers via MOCVD, and could open opportunities for future device manufacturing. -
8A.2 – kV-Class β-Ga2O3 Trench Schottky Barrier Diodes: Double Drift Layer Design and Breakdown Analysis
Abstract
This work presents β-Ga2O3 trench Schottky barrier diodes (TSBDs) with double drift layer structures, achieving a 34% lower on-resistance compared to conventional single drift layer structures, without compromising the off-state performance. The TSBDs exhibit a breakdown voltage of ~2.4 kV, after which the devices were observed to crack along the [010] crystallographic direction in β-Ga2O3. The mechanisms behind breakdown-induced cracking were investigated including using nanoindentation, which revealed that the cracking is due to relatively weak chemical bonding along the [010] direction. -
8A.3 – Vertical Schottky Barrier Diodes with Optical Floating Zone Growth of β-Ga2O3 Single Crystals and Electrical Defect Study
Abstract
This study reports the melt growth of β-Ga2O3 single crystals using the Optical Floating Zone (OFZ) technique, and defect analysis in these wafers. X-ray diffraction (XRD) rocking curves show a full width at half maximum (FWHM) of 230 arcsec and the chemical mechanical polished surfaces exhibit a low surface roughness of 1.1 nm. Schottky barrier diodes (SBDs) were fabricated on these substrates and deep-level transient spectroscopy (DLTS) measurements were performed to investigate defects within the bandgap. DLTS analysis revealed a dominant single deep-level trap at 0.69 eV below the conduction band, attributed to Fe impurities from the source material used for melt-growth. -
8A.4 – Gallium Oxide Trench Schottky Barrier Diodes with Field Plate Edge-Termination
Abstract
In this work, Gallium Oxide (β-Ga2O3) based trench Schottky barrier diodes (TSBDs) with field plate edge-termination are reported. The SiNx field plate edge-terminated TSBDs show an improvement in breakdown voltage up to 2.3 kV as compared to the unterminated structures of 1 kV. The electric field simulations show a reduction in peak electric field at the edge of the diodes when terminated with SiNx field plates. Reliability measurements were performed by reverse-bias step-stressing and observing the on-state performance post stressing. An increase in on-resistance for TSBDs with field plate edge termination up to 12% is observed when devices are stressed at 1 kV.