For the first time, Pd nanoparticle-functionalized, rGO nanosheet-modified 3D rod-like CuO (Pd–CuO/rGO) with a nanowire hierarchical structure was successfully synthesized using a facile hydrothermal strategy. Interestingly, the developed Pd–CuO/rGO sensor exhibited more prominent features compared with the CuO, Pd–CuO and CuO/rGO sensors towards trace NO₂ gas at room temperature (RT, 23 °C). In particular, the Pd–CuO/rGO sensor demonstrated an ultra-high response of 64.2 towards 100 ppm NO₂ gas at RT, which was approximately 3.4 times that of the pristine CuO sensor, 2.7 times that of the Pd–CuO sensor and 2 times that of the CuO/rGO sensor, respectively. Simultaneously, a response/recovery time of 10.7/9.2 s towards 10 ppm NO₂ gas at RT was indicated for the Pd–CuO/rGO sensor, and the extremely low limit of detection was down to 50 ppb, ensuringreal-time detection at a ppb-level NO₂ gas concentration. Furthermore, the fabricated sensors had reliable consistency, excellent repeatability and long-term stability. In addition to the contribution from the porous rGO-modified CuO providing abundant active places for gas adsorption and diffusion, Pd and partially oxidized Pd NPs that chemically and electronically sensitized the CuO supporter greatly improved the sensitivity and selectivity of the fabricated Pd–CuO/rGO sensor. Moreover, abundant surface oxygen vacancies were also to some extent beneficial for the sensing performance. Our scientific and systematic work has great potential for practical applications in extremely harsh environments.

Screw dislocations are generally considered to be one of the main causes of GaN-based device leakage, but so far, nearly no reports have focused on the effects of open-core screw dislocations on device leakage currents experimentally. In this paper, we use a conductive atomic force microscope to characterize the electronic properties of threading dislocations (TDs) in the GaN layer. The full-core screw dislocations and mixed dislocations are found to provide conductive paths for device leakage currents. In terms of the contribution to device leakage currents, the edge and open-core screw dislocations have smaller effects than the full-core screw dislocations and mixed dislocations. We use isotropic linear elasticity theory and density functional theory calculations to model the core atomic structures of TDs and calculate the corresponding electronic structures. The results show that screw dislocations with full-core structures are found to introduce both deep and shallow energy states within the energy gap dispersedly, while the open-core screw dislocations and the most edge dislocations introduce only shallow energy states. The calculated electronic structures of each type of dislocation are systematically compared and correlated with experimental observations. Our findings demonstrate that full-core screw dislocations and mixed dislocations in the GaN layer have a far more detrimental impact on device leakage than edge and open-core screw dislocations.

The self-powered photoelectrochemical components themselves featured advancements in operating independently without external supply. Ultimately, due to lack of assistance from the external bias, the photoelectrochemical response is commonly restricted by the deficient photo-quantum efficiency for the absence of carrier multiplication. This work demonstrates a self-powered photoelectrochemical photodetector based on CuO_x/AlGaN nanowires with staggered band structure and enhanced built-in potential for efficient exciton extraction. The generated multiple excitons within reach-through CuO_x layer could be speedily separated before Auger recombination. This yields a 131.5% external quantum efficiency and 270.6 mA W⁻¹ responsivity at 255 nm. The work confirms the role of multiple exciton generation in photoelectrochemical systems, offering a solution on paving path of advance for self-powered optoelectronics and weak-light UV imaging applications.

A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L⁻¹ to 2 mg L⁻¹, the sensitivity and detection limit of the sensor is 3.191 μA/mg L⁻¹ and 1.97 μg L⁻¹, respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection.

Micro-light emitting diodes (Micro-LEDs) based on III-nitride semiconductors have become a research hotspot in the field of high-resolution display due to its unique advantages. However, the edge effect caused by inductively coupled plasma (ICP) dry etching in Micro-LEDs become significant with respect to the decreased chip size, resulting in a great reduction in device performance. In this article, sector-shaped GaN-based blue Micro-LEDs are designed and fabricated. Additionally, the device performance of different size Micro-LEDs with passivation are investigated with respect to those without passivation. Several methods have been applied to minimize the etching damage near the edge, including acid-base wet etching and SiO₂ passivation layer growth. The room temperature photoluminescence (PL) results demonstrate that the light emission intensity of Micro-LEDs can be significantly enhanced by optimized passivation process. PL mapping images show that the overall luminescence of properly passivated Micro-LEDs is enhanced, the uniformity is improved, and the effective luminescence area is increased. The recombination lifetime of carriers in Micro-LEDs are increased by the usage of passivation process, which proves the reduction in non-radiative recombination centers in Micro-LEDs and improved luminescence efficiency. As a result, the internal quantum efficiency (IQE) is improved from 14.9% to 37.6% for 10 μm Micro-LEDs, and from 18.3% to 26.9% for 5 μm Micro-LEDs.