Light-emitting diodes (LEDs) with high response frequency and high power can be applied in visible light communication (VLC). This paper studies the response frequency and optical output power of the gallium nitride (GaN) based matrix micro-LED (μLED) for visible light communication. The blue-emitting GaN μLEDs with the format from 1×1 to 6×6 are fabricated and used to analyze the relationship between the matrix format and the response frequency, as well as the output optical power and the data transmission performance of the matrix μLED. The experimental and analysis results show that the GaN-based matrix μLED response frequency can be improved by an increase in the injection current density increased and a decrease in device capacitance. The experimental comparison result indicates that the −3 dB response frequency changed from 85 MHz to 401 MHz at a 60 mA injection current progressively increased as the matrix array size from 1×1 to 6×6，the 6×6 matrix μLED optical output power reaches a value of 356.7 mW.

A GaN-based vertical superjunction high electron mobility transistor (SJ HEMT) with a composite structure (CS-SJ HEMT) is proposed and analyzed by Silvaco TCAD to improve the breakdown voltage and specific on-resistance (R _onA ). In this paper, CS-SJ HEMT is compared with SJ HEMT with traditional structure (TS-SJ HEMT), SJ HEMT with only particular doping pillars (DP-SJ HEMT) and SJ HEMT with only special P-gate (SP-SJ HEMT). The particular doping pillars mean the doping concentration of n-pillar increases with a gradient from top to bottom, and the concentration of p-pillar is the same as the middle of n-pillar, which reduces the R _onA by only 4%. The special P-GaN cap layer can reduce the R _onA by 10%, and it can even increase the on-state current in the saturation region. The CS-SJ HEMT combines both doping pillars and special P-gate structures, and the R _onA can be reduced by 14%. By the optimized design, the R _onA can be reduced by 30% with BV = 2580 V, or the R _onA can be reduced by 21% with BV = 2720 V. These results show that the composite structure of SJ HEMT contributes to improving the BV and R _onA and propose a useful approach for improving the vertical HEMTs.

Deep ultraviolet (DUV) light-emitting diodes (LEDs) have attracted widespread attention in communication because of their lack of background noise interference in day-blind communications, but their low luminous efficiency and low response frequency cannot meet the requirements of non-visual optical communication systems. AlGaN-based micro-LEDs ( $\mu $ -LEDs) can provide high light output power (LOP) due to their smaller chip size, and they can also withstand high current density due to their enhanced current diffusion uniformity. Thus, matrix-type DUV $\mu $ -LEDs are effective candidates to enhance LOP and response frequency. In this work, a matrix-type AlGaN-based DUV communication LED with step-graded Al composition superlattice (SL) electron-blocking layer (EBL) at wavelength of 274 nm was designed, LOP and response frequency reached 45.4 mW and 414 MHz at 212 A/cm2 current density. After this SL EBL applied in the UV communication LED, hole injection capability was enhanced, high LOP and high response frequency make it be an ideal candidate for wireless communication applications.

Raman spectroscopy is a spectral analysis technique based on molecular vibration. It has gained widespread acceptance as a practical tool for the non-invasive and rapid characterization or identification of multiple analytes and compounds in recent years. In fruit quality detection, Raman spectroscopy is employed to detect organic compounds, such as pigments, phenols, and sugars, as well as to analyze the molecular structures of specific chemical bonds or functional groups, providing valuable insights into fruit disease detection, pesticide residue analysis, and origin identification. Consequently, Raman spectroscopy techniques have demonstrated significant potential in agri-food analysis across various domains. Notably, the frontier of Raman spectroscopy is experiencing a surge in machine learning applications to enhance the resolution and quality of the resulting spectra. This paper reviews the fundamental principles and recent advancements in Raman spectroscopy and explores data processing techniques that use machine learning in Raman spectroscopy, with a focus on its applications in detecting fruit diseases, analyzing pesticide residues, and identifying origins. Finally, it highlights the challenges and future prospects of Raman spectroscopy, offering an effective reference for fruit quality detection.

Due to environmental friendliness, small size, long lifetime, and adjustable light-emitting wavelength, AlGaN-based deep ultraviolet light-emitting diodes (DUV-LEDs) have great development potential in the fields of biochemical detection, sterilization and disinfection, and non-line-of-sight communication. After decades of research, AlGaN-based DUV-LEDs have significantly improved in the direction of luminous efficiency. However, the luminous efficiency of the present AlGaN-based DUV-LEDs is still at a low level compared with that of the fully commercialised nitride blue LEDs, making it difficult to meet the market demand. This paper first introduces the present development status of AlGaN-based DUV-LEDs and the reasons for the low luminous efficiency. Then from the preparation of AlGaN-based, AlGaN doping and the design of AlGaN-based DUV-LEDs structure to elaborate the research progress in recent years in the direction of improving the luminous efficiency of AlGaN-based DUV-LEDs. Finally discusses the challenges that the AlGaN-based DUV-LEDs are presently faced with, and their future opportunities for development.

Past studies have demonstrated the positive impact of step-graded p-type Al _x Ga _1-x N/GaN superlattice (SL) electron blocking layer (EBL) structures on the efficiency performance of ultraviolet (UV) GaN-based light-emitting diodes (LEDs). However, the optimal Al-grading structure of these SL EBLs remains unclear owing to a lack of systematic investigation. The present work addresses this issue by applying EBL composed of alternating half-peak, single-peak, and double-peak p-type Al _x Ga _1-x N/GaN SL structures with varying values of x ranging from 0.05 to 0.15 in 0.05 step increments. Simulation analysis is employed to obtain the internal quantum efficiency (IQE), energy band diagrams, polarization compensation factor, hole concentration, and electron concentration of GaN-based UV LEDs with three different SL-EBL structures. The results obtained at an injection current of 200 mA demonstrate that UV LEDs with double-peak SL-EBL structures provide the maximum IQE, which is ~38% greater than that of devices employing the conventional EBL in simulation experiment. This SL-EBL is demonstrated to improve the hole injection and electron overflow performance of GaN-based UV LEDs owing to the polarization charge and lattice mismatch at the p-Al _x Ga _1-x N/GaN interfaces. The reduced Al composition on the p-GaN side reduces the potential barrier of hole injection. Moreover, the predicted increase in the IQE of GaN-based UV LEDs with the optimal SL-EBL is verified experimentally.