To overcome the challenges faced by conventional laser lift-off and transfer methods for light-emitting III-nitride material systems, such as high processing costs and compatibility issues with long-wavelength devices, this study demonstrates centimeter-scale mass transfer of thin-film micro-LEDs using electrochemical (EC) etching and metal-metal bonding for heterogeneous integration. III-nitride micro-LED structures incorporating a sacrificial layer were epitaxially grown by metal-organic chemical vapor deposition (MOCVD). Following the fabrication of centimeter-scale micro-LED arrays with lateral device sizes ranging from 100 mu m to 3 mu m on the growth substrate, EC etching of the sacrificial layer and Au-Au flip-chip bonding were employed to mass transfer the submicron-thin devices onto Si substrates. The structural, optical, and electrical properties of the transferred devices were characterized using scanning electron microscopy, atomic force microscopy, cathodoluminescence, and electroluminescence, demonstrating preservation of material quality and device performance before and after transfer.

We report a scalable, low-damage, and high-throughput process for monolithic transfer of III-nitride micro-LED arrays using selective electrochemical etching and wafer bonding. A highly Si-doped n-GaN sacrificial layer enables rapid and uniform release while preserving device integrity, resulting in atomically smooth lift-off surfaces suitable for subsequent processing. Fully fabricated vertical micro-LED arrays with mesa sizes from 100 & times; 100 mu m(2) down to 3 & times; 3 mu m(2) are released and transferred to silicon carrier wafers in a single step, maintaining precise spatial registration without conventional laser lift-off or serial pick-and-place methods. Transferred devices exhibit low reverse leakage, uniform current injection and emission, and enhanced optical output due to the thin-film flip-chip architecture, with minimal degradation in spectral performance. This approach provides a promising pathway for the scalable heterogeneous integration of III-nitride devices for micro-displays, optical communications, and sensing applications.

The electrical characteristics under forward- and reverse-bias conditions of III-nitride blue and green micro-light-emitting diodes (μLEDs) are analyzed. A fitting model is proposed to determine the contributions of reverse leakage current and the effectiveness of sidewall treatments. Moreover, the forward-bias currents of the μLEDs are examined using the extracted ideality factor to examine the impacts of sidewall defects. The results show that sidewall treatments are highly effective for suppression of leakage currents. From the efficiency perspective, higher wall-plug efficiency (WPE) than external quantum efficiency (EQE) is observed when the operating voltage is lower than the photon voltage in both blue and green 20 × 20 μm2 devices. This enhancement of the WPE over the EQE is due to the suppression of Shockley–Read–Hall (SRH) nonradiative recombination. These observations indicate that μLEDs with sidewall treatments not only improve optical performance but also further enhance the electrical performance of devices by suppressing the leakage current paths due to SRH nonradiative recombination processes.

We demonstrate the first micro-LED-(10x10 µm2)-based quantum-random-number generator at 9.375 Gb/s and 0.2 pJ/bit, which successfully passes NIST randomness test. The high generation rate and low power consumption are beneficial for low-cost quantum communications.

Thin-film III-nitride micro-LEDs were fabricated by electrochemically etching a sacrificial layer, enabling substrate lift-off with preserved material quality, presenting an efficient and scalable solution for micro-LED mass transfer.

We present a high-performance GaN-based vertical-cavity surface-emitting laser with a long cavity (70 lambda), nanoporous GaN distributed Bragg reflector (DBR), and topside dielectric lens, achieving room-temperature continuous-wave operation up to thermal rollover at 34 kA cm-2 and a peak output power of 2.7 mW. Process optimizations significantly improved the lens surface quality, reducing optical losses. The long cavity improved thermal management, leading to a measured thermal impedance of 607 K W-1, the lowest reported for GaN vertical-cavity surface-emitting lasers (VCSELs) with a nanoporous DBR. Spatial mode analysis revealed structured Laguerre-Gaussian-like patterns, with evidence of coherent speckle. These results demonstrate the viability of long-cavity designs for high-power GaN VCSELs.

Enhancing light-matter interactions at the nanoscale is foundational to nanophotonics, with epsilon near zero (ENZ) materials demonstrating significant potential.High-quality (Q) factor resonances maximizing these interactions are typically realized in photonic crystals requiring sub-50 nm precision nanofabrication over large areas, limiting scalability and increasing complexity. Mie resonances offer an alternative but are constrained by low Q factors due to the scarcity of high refractive index materials, necessitating large refractive index changes for effective resonance switching and limiting dynamic reconfigurability. We overcome these limitations by embedding Mie resonators within ENZ media, thereby enhancing Q- factors, mitigating geometric dispersion and fabrication challenges, and maximizing optical reconfigurability. We introduce three resonator-ENZ configurations - voids in AlN, Ge in SiO_2, and intrinsic InSb in doped InSb - spanning from low-loss phononic to lossy plasmonic ENZ modes.Using novel epitaxial regrowth techniques, we achieve significant Q-factor improvements over non-embedded resonators. Notably, an air-based Mie resonator embedded in AlN supports resonant Q-factors exceeding 100, with negligible geometric dispersion across sizes from 800 nm to 2,800 nm. Additionally, we demonstrate dynamic reconfigurability of intrinsic InSb resonators by thermally tuning the ENZ wavelength over a 2μm range in the mid-infrared (11-16 μm) wavelength regime. These results showcase the potential of Mie resonators embedded in ENZ media for high-fidelity sensors, thermal emitters, and reconfigurable metasurfaces, bridging theoretical predictions with practical applications, advancing the development of dynamic, high-Q optical devices.

GaN-based distributed feedback (DFB) laser diodes are narrow linewidth sources promising for integration into low-size, weight, and power photonic circuits. There is a need to improve the linewidth, expand the availability of technologically useful wavelengths, and increase the power and efficiency for several applications. BluGlass presents advancements in visible wavelength DFB lasers. We will show measured device results achieving higher side-mode-suppression ratio of 40 dB and a peak full-width half maximum under 3 pm demonstrating near single frequency emission. Devices targeting critical atomic transition wavelengths for clocks, quantum computing, and other cold physics applications are covered spanning from 408 nm to 470 nm. A path toward narrow-band high-power DFB sources will be presented with preliminary data on gain in GaN-based semiconductor optical amplifiers.

We report on the successful demonstration of an all metalorganic chemical vapor deposition (MOCVD) grown fully transparent tunnel junction (TJ) germicidal UV LED, resulting from the use of a lightly doped n--AlGaN contact layer enabling rapid MOCVD growth optimization. We found that the optimal condition for LED performance was a 3 nm p++-Al0.6Ga0.4N / 9 nm n++-Al0.65Ga0.35N TJ above a 20 period 1 nm p-Al0.8Ga0.2N/ 1 nm p-Al0.2Ga0.8N short-period superlattice (SPSL). We observed a peak external quantum efficiency (EQE) of the λ = 294 nm TJ UV LED of 12.1%, and an EQE of 10.4% at 20 A/cm2 and 9.1% at 35 A/cm2, with an excess voltage of 1.5 V at 1 A/cm2.

Wafer-scale III-nitride epitaxial layers are selectively lifted off via an innovative electrochemical etching method, allowing epilayers to achieve ultra-high relaxation, preserved quality, and sub-nanometer root-mean-square interface roughness for diverse applications, as demonstrated with micro-light-emitting diodes.

Gallium nitride (GaN) microcavity light-emitting diodes (MCLEDs) have demonstrated useful properties for visible light communication (VLC) via improved directionality is useful for free space transmission, and their limited fiber mode dispersion leads to faster modulation bandwidth in fiber communication compared to standard LEDs. Here, we report the first demonstration, to the best of our knowledge, of resonant cavity effects observed in a LED with an air/GaN interface as top mirror with a top GaN tunnel junction (TJ) contact, and an epitaxial nanoporous distributed Bragg reflector (NPDBR) as bottom mirror. The abrupt top air/GaN interface offers improved light extraction compared to dielectric DBRs and simplifies the topside contact.

Quantum random number generators (QRNGs) leverage the inherent unpredictability of quantum mechanical phenomena to produce random numbers. However, the performance of many QRNGs is hindered by limitations such as low generation rates and the bulkiness of systems utilizing single-photon detectors (SPDs). In this study, we present a QRNG that addresses these challenges by using a micro-LED as an entropy source, utilizing the intensity fluctuations of spontaneous emissions. By applying post-processing techniques, our 5 × 5 µm 2 micro-LED-based system achieves a PD bandwidth-limited generation rate of 9.375 Gbit/s while successfully passing the required randomness tests outlined by the National Institute of Standards and Technology (NIST). Importantly, systematic testing across micro-LEDs of varying sizes demonstrates consistently high performance, highlighting the robustness of this approach. The compact, small footprint, scalable design, and surface emission characteristics of micro-LEDs pave the way for the development of parallel QRNG-integrated chips, which hold the potential to deliver ultra-high random number generation rates in practical, miniaturized platforms.

The nonuniform hole distribution between InGaN quantum wells (QWs) of light emitting diodes (LEDs) has a negative impact on LED efficiency. The uniformity can be increased by using lateral hole injection through sidewalls of V-defects, which form at threading dislocations. However, the inherent coupling between the V-defects and dislocations might affect efficiency of the hole injection and nonradiative recombination. In this work, we have tested the possible impact of the dislocations on the injection and recombination by means of scanning near-field electroluminescence and photoluminescence spectroscopy on single green-emitting InGaN QW LEDs containing large (∼0.5 μm) V-defects. The measurements have not provided any evidence of a lower hole injection efficiency or enhanced nonradiative recombination at the dislocations located at the V-defect facets or their apexes. This shows that large V-defects are excellent volumetric injectors for long wavelength InGaN LEDs. Furthermore, it was established that V-defects are preferential hole injectors even in single quantum well devices. Compared to vertical injection, the V-defect injection allows lowering the operating voltage, which should contribute to an enhanced wall plug efficiency.

Enhancing light-matter interactions at the nanoscale is foundational to nanophotonics, with epsilon-near-zero (ENZ) materials demonstrating significant potential. High-quality factor (Q) resonances that maximize these interactions are typically realized in photonic crystals requiring sub-50 nm precision nanofabrication over large areas, limiting scalability and increasing complexity. Mie resonances offer an alternative but are constrained by low Q-factors due to the scarcity of high-refractive index materials, necessitating large refractive index changes for effective resonance switching and limiting dynamic reconfigurability. We overcome these limitations by embedding Mie resonators within ENZ media, thereby enhancing Q-factors, mitigating geometric dispersion and fabrication challenges, and maximizing optical reconfigurability. We introduce three resonator-ENZ configurations: voids in AlN, Ge in SiO2, and intrinsic InSb in doped InSb─spanning from low-loss phononic to lossy plasmonic ENZ modes. Using novel epitaxial regrowth techniques, we achieve significant Q-factor improvements over nonembedded resonators. An air-based Mie resonator embedded in AlN supports resonant Q-factors exceeding 100, with negligible geometric dispersion across sizes from 800  to 2800 nm. Additionally, we demonstrate dynamic reconfigurability of intrinsic InSb resonators by thermally tuning the ENZ wavelength over a 2 μm range in the mid-infrared (11-16 μm) wavelength regime. These results showcase the potential of Mie reonators embedded in ENZ media for high-fidelity sensors, thermal emitters, and reconfigurable metasurfaces, bridging theoretical predictions with practical applications and advancing the development of dynamic, high-Q optical devices.

We report a selective electrochemical etching-based liftoff technique for III-nitride thin films using a heavily Si-doped sacrificial layer. This method enables the detachment of the millimeter-sized III-nitride thin films with tunable thickness from arbitrary substrates, achieving minimal damage and sub-nanometer liftoff surface roughness, offering more flexibility than traditional liftoff methods such as laser liftoff. Structure and optical characterization confirm the preservation of the crystal quality throughout the process. Notably, InGaN-based blue mu LEDs were lifted off and transferred onto Si substrates, maintaining excellent optoelectronic properties, showing great potential in mass transfer of nitride-based mu LEDs for micro-display. This proof-of-concept demonstration highlights a scalable, low-damage pathway for heterogeneous integration of III-nitride materials onto diverse platforms for advanced optoelectronic applications.

We have successfully demonstrated InGaN/GaN edge-emitting laser diodes (EELDs) on a fully coalesced epitaxial lateral overgrown film from a c-plane GaN substrate. We achieve a high aspect ratio, and low defect density wing region covering 75%-88% of the substrates' surface, which is amongst the largest reported areas in the literature. The devices at the wing region exhibit a threshold current density of 3.63 kA cm-2 at 408 nm, and an improved laser performance compared to the high defect density region is confirmed. Based on this work, it is promising that high performance, cost-efficient c-plane InGaN/GaN EELDs can be realized.

The quantum efficiency of micro-light emitting diodes (micro-LEDs) is lower than that of large area LEDs. This efficiency reduction is typically attributed to the nonradiative Shockley–Read–Hall recombination at the surface defects and current leakage through the sidewall region without a clear distinction between these effects. In this work, we attempt to find out which of these phenomena is most critical for the reduced efficiency of micro-LEDs. This has been done by mapping electroluminescence (EL) and photoluminescence (PL) and measuring PL dynamics in blue GaN micro-LEDs fabricated by dry etching. It has been found that in the as-etched device, the EL intensity is much lower than in devices with KOH etching and atomic layer deposition of SiO2. This effect is especially pronounced close to the sidewalls. On the other hand, PL decay times are similar in as-etched and passivated devices, both in their center and at the sidewalls. This allows concluding that the main mechanism of the reduced efficiency of micro-LEDs fabricated by dry etching is the current leakage in the sidewall region and not the nonradiative recombination. The KOH etching has been found to be the most efficient means to eliminate the current leakage.