Jinchai Li

Flexible transparent conductive film is essential in modern optoelectronic applications. However, how to obtain high‐output and high‐quality transparent conductive electrode (TCE) materials at low cost still remains challenging. This study demonstrates a successive synthesis system based on cyclic repeated‐batch operation to achieve low‐cost, high‐output production of high‐quality Cu nanowires (NWs), with an optional Ni‐shell coating step incorporated into the workflow for oxidation protection. The combination of precursor supplying controller and product collector enables the cyclic synthesis of Cu/Cu@Ni NWs. A 3D sonication printer is designed for non‐contact and uniform printing of a conductive film on arbitrary target substrates. The fabricated flexible Cu NW TCEs exhibit excellent optoelectronic performance (34.46 Ω sq ⁻¹ @ 85.92% transmittance at 550 nm, with a haze of 1.40%), outstanding large‐area uniformity (20 × 20 cm ² ) and good mechanical stability, while Ni‐shell coating effectively enhances the oxidation resistance of the Cu NWs. Flexible transparent touch screens based on Cu NW TCEs are further demonstrated with resistive and self‐capacitive sensing structures. Complex motion control and pen writing can be achieved fluently in both flat and curved states. This work shows great potential in future touch displays, for example, the new‐generation smartphones with transparent, rollable, and extendable touch screens.

Yellow–green InGaN micro-light-emitting diodes (micro-LEDs) are attractive transmitters for visible-light communication, yet high-In-content quantum wells usually impose a trade-off among efficiency, optical power, and modulation speed. Here, we report c-plane single-quantum-well InGaN micro-LEDs emitting near 545 nm that combine milliwatt-level output at high-current density with gigahertz-class small-signal modulation. Devices with lateral sizes of 40 and 60 μm exhibit peak external quantum efficiencies (EQEs) of 5.36% and 5.35%, respectively, and retain EQEs of 2.84% and 2.83% at 1000 A cm−2. The 40 μm device reaches a maximum −3dB bandwidth of 1.55 GHz and maintains gigahertz-class bandwidth from a high operation temperature (300–375 K). We also demonstrate 2.0 Gbit/s free-space non-return-to-zero on–off keying transmission with an estimated bit-error rate below the 7% overhead hard-decision forward-error-correction limit. These results show that c-plane yellow–green InGaN micro-LEDs can provide compact, efficient, and thermally robust transmitters for high-speed free-space visible-light links.

In this study, we propose and investigate three atomic configurations of magnesium (Mg)-induced GaN inversion domain superlattices (denoted as IDBNa, IDBNb and IDBNc) using first-principles density functional theory. Detailed electronic structure analysis reveals that periodic polarity inversion at inversion domain boundaries induces the formation of two-dimensional carrier gases and periodic band bending. These features also lead to local band-gap narrowing and modify the spatial distribution of electronic structure along the c -axis. Defect calculations show that Ga vacancies and substitutional Mg atoms typically form near Mg intercalations, whereas N vacancies tend to localize farther away under different ambient growth conditions. These defects exhibit strong spatial localization, significantly affecting the local electronic structure. Furthermore, Mg segregation at inversion boundaries is found to be energetically favorable at fractions below or around 3/2 monolayers, maintaining near-monolayer structural characteristics. As Mg segregation increases, the built-in polarization fields are gradually compensated, which reduces band bending and modifies the spatial distribution of electronic structure compared with the non-segregated IDBNc superlattices. The combined effects of structural polarity inversion, localized defect formation, and Mg segregation provide critical insights into band structure modulation in Mg-induced GaN inversion domain superlattices. These findings provide a theoretical foundation for understanding the electronic structure, defect characteristics and the formation mechanism of Mg-induced GaN inversion domain superlattices, offering pathways for interface and defect engineering to optimize p -type conductivity in high-performance GaN-based electronic and optoelectronic devices.

A transfer learning based dual-channel convolutional neural network (TLD-Net) with a cyclic matrix-based feature representation is proposed for robust Micro-LED performance prediction under limited data and application-specific scenarios.

Efficient long-wavelength nano-light-emitting diodes (nano-LEDs) are essential for ultrahigh-density monolithic RGB micro-displays, yet their efficiency usually deteriorates as device size shrinks because sidewall-related nonradiative recombination becomes increasingly important. Here, we demonstrate electrically injected planar InGaN amber nano-LEDs with a circular mesa diameter of ∼840 nm fabricated by a conventional top-down process with conformal ALD-Al2O3 sidewall passivation. The device emits at 608 nm and exhibits an ultralow reverse leakage current of ∼10−14 A at −5 V. A peak external quantum efficiency of 10.1% is achieved at ∼12 A/cm2, exceeding that of a 20 μm device from the same wafer (∼9.8% at ∼4 A/cm2). Analysis using an ABC model indicates that downscaling increases the sidewall-related SRH term, but this penalty is overcompensated by enhanced light extraction efficiency in the nanoscale mesa. The fluorescence lifetime imaging microscopy mapping further reveals spatially resolved carrier dynamics that are closely correlated with strong carrier localization in the high-In-content red-emitting quantum wells, which helps suppress sidewall nonradiative recombination. These results establish top-down long-wavelength III-nitride nano-LEDs as a viable route toward ultrahigh-resolution monolithic micro-displays.

Sidewall damage induced by dry etching fundamentally limits the efficiency of InGaN-based micro light-emitting diodes (Micro-LEDs), yet its nanoscale structure and layer-specific impact remain insufficiently quantified. Herein, we report a comprehensive numerical investigation of carrier transport and recombination mechanisms in nitride-based Micro-LEDs with lateral nanoscale localized damage using finite-element simulations. The results demonstrate that localized damage in the MQWs severely degrades the external quantum efficiency, primarily due to concentration-gradient-driven lateral diffusion of carriers toward sidewall defects and enhanced Shockley–Read–Hall recombination. Localized damage in the electron blocking layer causes non-uniform current-density distribution and reduced carrier injection efficiency under high current densities. Our simulations of etching-induced nanoscale sidewall damage clarify the mechanisms of performance degradation in III-nitride micro-LEDs and provide layer-resolved microscopic guidelines for improving the performance and reliability of InGaN micro-LEDs.

Achieving high hole conductivity in high-Al-content p-type AlGaN remains a critical challenge for deep-ultraviolet (DUV) optoelectronics. In this work, we systematically investigate the electronic structures and hole transport mechanisms in three Mg-doped Al _0.75 Ga _0.25 N configurations: alloy, (GaN)₁/(AlN)₃ superlattice (SL), and GaN quantum dots (QD) by performing the first-principles calculations. While the alloy configuration exhibits the highest hole mobility, it is limited by a large activation energy (367 meV). The QD configuration shows the lowest activation energy but is plagued by an extremely high ionized impurity (IMP) scattering rate, resulting in the poorest mobility (0.01 cm ² V ⁻¹ s ⁻¹ ). Consequently, the SL configuration presents a balanced and promising candidate. We further demonstrate that the hole transport in the SL can be optimized through site-selective Mg doping within the AlN layer, which concurrently reduces the hole effective mass, suppresses the dominant IMP and polar optical phonon scattering rates by over an order of magnitude, and lowers the activation energy, thereby enhancing the mobility to increased to 18.9 cm ² V ⁻¹ s ⁻¹ . This study elucidates the carrier scattering mechanisms across different doping architectures and proposes a feasible doping-site-engineering to overcome the key limitation in p-type conductivity of high-Al-content AlGaN, paving the way for efficient DUV optoelectronic devices.

Achieving InGaN quantum wells (QWs) with high indium compositions for red emission presents significant challenges. One challenge is that the red peak is often accompanied by a short-wavelength emission with increased current injection. In this work, such dual-peak emissions in InGaN red multiple QWs (MQWs) were investigated using cross-sectional cathodoluminescence and scanning transmission electron microscopy. This was attributed to the compositional pulling effect. A peak shift from 570 to 600 nm, in conjunction with increased indium composition, was observed across the MQWs from the bottom to the top. By controlling the growth temperature of the individual QWs, short-wavelength emission was suppressed. As a result of this, InGaN red micro light-emitting-diodes (Micro-LEDs) were fabricated, showing a single red emission peak up to a current density of 100 A/cm2 (612 nm) and a peak external quantum efficiency of 7.9% at 5.2 A/cm2. This study not only reveals the presence of the CPE in red InGaN MQWs of high indium compositions but also demonstrates a remedy to achieve single-peak red emission even under high current density operation.