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GaN-based light-emitting diodes (LEDs) have attracted widespread attention owing to their advantages of high efficiency and brightness, stable emission and full color emission. However, only a few studies have reported LEDs with bidirectional driving. Herein, we first fabricated an Au/i-Ga2O3/n-GaN heterojunction LED with a striking electrical performance of bidirectional DC driving. The results of I–V tests indicated that the LED possesses excellent rectification characteristics. The LED exhibited an extremely low leakage current of 1.6 × 10−11 A at ambient temperature, which increased to 4.3 × 10−9 A at 100 °C. In addition, electroluminescence (EL) analysis further confirmed the robust thermal stability of this heterojunction LED. It is noteworthy that the Au/i-Ga2O3/n-GaN heterojunction LED contains bidirectional DC driving. When the forward current is injected, this LED exhibits the strongest ultraviolet emission (376 nm) at 90 mA, and the peak position of EL spectra remains consistent with the temperature ranging from 50 to 90 °C. When reverse current is injected, the LED mainly emitted mixed yellow-green light, and the color coordinate changed from (0.336, 0.363) to (0.303, 0.350). With the increase in external temperature to 80 °C, the EL intensity reached as high as 95% of that at ambient temperature. This finding not only adds a feasible strategy to fabricate GaN-based diodes with intriguing bidirectional DC driving but also opens up a way for the development of special lighting semiconductor devices. [ABSTRACT FROM AUTHOR]

This paper proposes a Fiber Bragg Grating (FBG) stress detection technology based on Empirical Mode Decomposition (EMD) for suspended permanent magnet maglev box girder, which is used to detect the stress of the track box girder when the vehicle passes through, check whether the stress is within the safe range, and ensure the operation safety and stability of vehicles. Considering the influence of strong magnetic field and electromagnetic interference, the FBG grating sensing stress detection scheme without electricity on the track is adopted, and a test point is respectively arranged at the travel position of the upper and lower guide wheels. The FBG test point is subject to both low-frequency flexure stress and high-frequency guide wheel stress, and the EMD method is used to separate the two stresses. The experimental results show that the test results of vehicle passing stress in line with expectations. The stress detection technology for track box girder described in this paper can effectively ensure the health of track box girder and the operation safety of vehicles. [ABSTRACT FROM AUTHOR]