Size-dependent capacitance study on InGaN-based micro-light-emitting diodes

Yang, Wei and Zhang, Shuailong and McKendry, Jonathan and Herrnsdorf, Johannes and Tian, Pengfei and Gong, Zheng and Ji, Qingbin and Watson, Ian and Gu, Erdan and Dawson, Martin and Feng, Liefeng and Wang, Cunda and Hu, Xiaodong (2014) Size-dependent capacitance study on InGaN-based micro-light-emitting diodes. Journal of Applied Physics, 116 (4). 044512. ISSN 0021-8979 (

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We report a detailed study on size-dependent capacitance, especially the negative capacitance (NC), in InGaN-based micro-pixelated light-emitting diodes (μLEDs). Similar to conventional broad-area LEDs, μLEDs show NC under large forward bias. In the conventional depletion and diffusion capacitance regimes, a good linear relationship of capacitance with device size is observed. However, the NC under high forward bias shows slight deviation from above-mentioned linear relationship with device size. This behaviour can be understood if the effects of current density and junction temperature on NC are considered. The measured temperature dependence and frequency dispersion of the capacitance underpin this point of view. The NCs of two reference broad-area LEDs were also measured and compared with that of μLED clusters with the same total size. A stronger NC effect is observed in the μLED clusters, which is attributed to the increased number of sidewall defects during fabrication process.