Session Index

Ultra wide band gap AlGaN materials are key elements in widely used LED and HEMT devices. However, p-type doping still remains a bottleneck to exploit their properties fully. In this work, a broad range of growth conditions has been explored for the fabrication of Mg-doped (Al,Ga)N layers by molecular beam epitaxy. In particular, through different epitaxial processes, benefitting from the use of two nitrogen sources (N2 or NH3) and the possibility to perform above band gap light excitation of the surface during growth, a large series of samples have been fabricated and compared using optical, structural and electrical characterizations.

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The development of next-generation VR, MR, and XR displays relies on advances in GaN-based micro-LEDs with optimized nanorod architectures. 3D FDTD simulations demonstrate that changes in nanorod geometry significantly affect internal quantum efficiency and vertical light extraction efficiency, highlighting the importance of simulation in device optimization. Precision etching enables the fabrication of these advanced nanorod structures. Micro-PL and TRPL spectroscopy reveal that photon recycling (PR) greatly enhances spontaneous emission, achieving an 11-fold increase in luminous output compared to non-optimized counterparts. This combination of simulation-based design and PR elevates micro-LED performance for immersive and energy-efficient displays.

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We propose a non-contact micro-LED inspection method using the photovoltaic effect. By measuring open-circuit voltage (Voc) under different light sources, devices can be classified as normal, open, short, leakage, or high-Vf. Results show short and open defects are easily identified, while high-Vf devices require analyzing Voc versus optical intensity. The method offers an efficient alternative for large-scale micro-LED screening.

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(11-22) AlN were grown by MOVPE on m-plane sapphire using face-to-face-annealed sputtered-AlN templates (0.2–2 μm). AFM imaging indicated a smooth surface; X-ray rocking curves assessed crystallinity. Room-temperature, unpolarized Raman resolved E₂(low), quasi-TO, E₂(high), E₁-TO, and quasi-LO modes; sapphire peaks were identified. Increasing thickness redshifted quasi-TO and E₂(high), evidencing strain relaxation.

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We developed III-nitride quantum dot (QD) uniform arrays using MOCVD, forming single InGaN QDs at the apex of six-fold and three-fold symmetric GaN pyramids via a selflimited growth mechanism. This method enables precise control of QD position, size, and symmetry, crucial for high-purity single-photon and polarization-entangled photon generation.
We also fabricated GaN hexagonal microrods and triangular prisms supporting whispering gallery and superscar modes, respectively, achieving room-temperature exciton-polariton condensation. These advances in QD symmetry control and microcavity engineering pave the way for integrated quantum photonic and polaritonic devices.


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Gallium nitride (GaN) has become central to wide band gap power electronics, with decades of progress driving its adoption in sub-1kV applications and establishing it as a preferred choice for low-voltage systems. Silicon carbide (SiC) currently dominates the 1-3kV range, while gallium oxide (Ga2O3), with its ultra-wide band gap and higher breakdown strength, promises operation beyond both GaN and SiC. This raises a key question: which material will shape the future of high-voltage power electronics?
This talk will compare GaN, SiC and Ga2O3 across different voltage regimes, highlighting their performance advantages as well as key challenges in reliability, scalability and thermal management. Emphasis will be placed on high-voltage device architectures, defect-driven degradation, and emerging strategies such as heterogeneous integration, providing insights into pathways for next-generation, energy-efficient power conversion systems.

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In this work, isolation techniques for AlGaN/GaN high electron mobility transistors (HEMTs) are systematically optimized. To enhance isolation and reduce damage from processes such as ICP-RIE etching, ohmic annealing is performed before ion implantation, followed by CF₄ surface treatment. The optimized devices exhibit a five-order-of-magnitude improvement in the On/Off current ratio, primarily driven by a substantial reduction in gate leakage current. These results indicate better channel control and effective leakage suppression, making this approach highly promising for high-power applications.

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A GaN-based metalens collimator (MC) is designed to convert a light-emitting dipole
to a plane wave. Optical simulations predicted that the far-field divergence angle can be reduced
below 10̊ for the dipole emission of the focus. However, when random off-focus dipoles are
taken into account, the overall enhancement declines significantly. We fabricated MC mosaic
partitions of different widths on the backside of light-emitting diode (LED) epitaxy to optimize
the overall enhancement. Angle-resolved photoluminescence measurements showed that the
frontal luminance of micro-LED with a 4-μm MC mosaic was boosted by 2.84 times compared
to the reference sample without MC.

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Thick semi-insulating gallium nitride layers doped with magnesium were fabricated on conductive ammonothermal gallium nitride substrates by magnesium ion implantation followed by ultra-high-pressure annealing at 1450 degrees Celsius for twenty-five hours under one gigapascal of nitrogen. Secondary ion mass spectrometry revealed “box-like” magnesium profiles with nearly constant concentration extending ten to twelve micrometres, enabling full compensation of silicon and oxygen donors. Covering the implanted surface reduced magnesium out-diffusion and increased penetration depth. Structural analyses confirmed preservation of crystalline quality and confinement of implantation-induced defects, providing a robust and cost-effective alternative to manganese-doped substrates for high-performance gallium nitride-based electronics.

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This research investigates the performance improvement of blue QLEDs by
introducing ZnO nanoparticles (ZnO NPs) as a charge control layer (CCL) between stacked
quantum dot emissive layers. The incorporation of the CCL effectively enhances the device’s
brightness and efficiency, achieving a maximum luminance (Lmax) of 102,029 cd/m² and a peak
current efficiency (CEmax) of 3.13 cd/A. These results demonstrate the significant impact of
CCL integration on boosting blue QLED performance, particularly in terms of luminance
enhancement and charge balance optimization.

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GaN-based laser diodes (LDs) are vital for next-generation displays and communications, yet achieving efficient long-wavelength operation remains challenging. We investigate InGaN quantum wells (QWs) of varying thickness and reveal that wide QWs enable lasing up to 20 nm longer than thin-QW counterparts of identical composition. Optical studies show that spontaneous emission originates from highly excited states, while population inversion and lasing occur only from lower excited states. This distinction between electroluminescence and optical gain overturns conventional assumptions and highlights wide-QW as a promising route toward long-wavelength LDs, if strain-related issues can be mitigated.

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