Palenskis Vilius, Matukas Jonas, Glemža Justinas, Pralgauskaitė Sandra
Institute of Applied Electrodynamics and Telecommunications, Vilnius University, Saulėtekio av. 3, LT-10257 Vilnius, Lithuania.
Materials (Basel). 2021 Dec 21;15(1):13. doi: 10.3390/ma15010013.
Low-frequency noise investigation is a highly sensitive and very informative method for characterization of white nitride-based light-emitting diodes (LEDs) as well as for the evaluation of their degradation. We present a review of quality and reliability investigations of high-power (1 W and 3 W) white light-emitting diodes during long-term aging at the maximum permissible forward current at room temperature. The research was centered on the investigation of blue InGaN and AlInGaN quantum wells (QWs) LEDs covered by a YAG:Ce phosphor layer for white light emission. The current-voltage, light output power, and low-frequency noise characteristics were measured. A broadband silicon photodetector and two-color (blue and red) selective silicon photodetectors were used for the LED output power detection, which makes it possible to separate physical processes related to the initial blue light radiation and the phosphor luminescence. Particular attention was paid to the measurement and interpretation of the simultaneous cross-correlation coefficient between electrical and optical fluctuations. The presented method enables to determine which part of fluctuations originates in the quantum well layer of the LED. The technique using the two-color selective photodetector enables investigation of changes in the noise properties of the main blue light source and the phosphor layer during the long-term aging.
低频噪声研究是一种用于表征基于氮化镓的白色发光二极管（LED）及其退化评估的高度灵敏且信息丰富的方法。我们综述了高功率（1W和3W）白色发光二极管在室温下最大允许正向电流下长期老化过程中的质量和可靠性研究。该研究集中于对覆盖有YAG:Ce荧光粉层以实现白光发射的蓝色InGaN和AlInGaN量子阱（QW）LED的研究。测量了电流-电压、光输出功率和低频噪声特性。使用宽带硅光电探测器和双色（蓝色和红色）选择性硅光电探测器来检测LED的输出功率，这使得能够区分与初始蓝光辐射和荧光粉发光相关的物理过程。特别关注了电波动和光波动之间同步互相关系数的测量和解释。所提出的方法能够确定波动的哪一部分起源于LED的量子阱层。使用双色选择性光电探测器的技术能够研究长期老化过程中主要蓝光源和荧光粉层噪声特性的变化。
