Traditional AlGaN electron blocking layer (EBL) has significant limitations in reducing electron leakage and enhancing electron injection, especially in high-Al-content environments. This study presents an EBL that combines superlattice (SL) and multi-gradient structures, aiming to enhance the performance of deep ultraviolet (DUV) light-emitting diodes (LEDs). Simulations were performed using the semiconductor device advanced physics model (APSYS) software, and comparisons were made with conventional high-Al content AlGaN EBL and SL EBL. The results indicate that the combination of SL and multi-gradient EBL significantly increases the electron barrier height, suppresses electron leakage, and enhances hole injection efficiency, leading to a 42.4
Excitons play an important role in semiconductor physics, whereas their electrical characteristics have rarely been explored. Here, AC differential capacitance response spectroscopy is applied to GaN-based multi-quantum-well (MQW) laser diodes (LDs) to investigate the transition-bound excitons. The capacitance response aligns with a modified rate equation, exhibiting negative activation energy, attributed to a sub-stable transition-bound state. Temperature dependent measurements yield binding energies of the transition-bound state consistent with weakly confined excitons in III–V quantum structures. These results confirm transition-bound excitons under continuous electrical excitation. As a comparison, the differential capacitance response of GaAs-based MQW LDs has shown that there is no negative activation energy, which further confirms the transition-bound excitons in GaN-based MQW LDs at room temperature. In addition, simulations of GaN-based MQW LDs’ capacitance response match experimental results well.
The aim of this study was to develop a simple, rapid, and reagent-free method for predicting the content of typical monocyclic aromatic hydrocarbons, benzene and toluene, in water using fluorescence spectroscopy data, chemometric methods, and random forest (RF) regression models. This was achieved through the reproducibility testing of fluorescence spectra configured at various concentrations of benzene and toluene, where the relative standard deviation (RSD) was approximately 5
We propose a distributed fiber sensor based on optical frequency domain reflectometry (OFDR) for strain measurement on a wind turbine blade. Due to the varying cross sections along the heterotypic blade, the strain distribution is nonlinearly demonstrated in experiment as estimated and predicted in numerical analysis. Negative strains (compression) and positive strains (tension) are detected in the 177–198 cm and 224–245 cm regions of the fiber, respectively. Moreover, responsivities of −0.775 71 µε/g and 0.599 53 µε/g at 195 cm and 228 cm are proved to be inversely proportional to the local cross sections, with a linearity quantified by R2 values of 0.999 87 and 0.999 9. This technique provides an effective method to characterize strain in heterotypic structure, showing potential in defect positioning by stress concentration as well.
The chemical oxygen demand (COD) online monitoring sensor, based on the spectral absorption, shows outstanding advantages in water quality monitoring, pollution source tracing, and environmental protection inspection. However, there are several factors that influence the stability and accuracy of the sensor detection in practical applications. Therefore, they must be carefully considered. This research analyzes the impact of changes in physical characteristics, chemical composition, and external environmental interference on the output result of the optical COD sensor systematically and comprehensively, from different fields including electronic technology, sensor technology, composition analysis, and environmental condition analysis, through both theoretical and experimental approaches. This study will provide guidance for the scientific research, product development, and upgrading of the optical water quality sensor, and provide reference for the long-term use, operation, and maintenance of the sensor.
