Using GaN-based light-emitting diodes (LEDs) as a radio source for visible light communication (VLC) is one of alternative choice in a high-speed data system. However, the spontaneous radiative recombination lifetime in the multiple quantum wells (MQWs) usually restrict the modulation bandwidth of LEDs. For LEDs accompanied photonic crystal (PhC) structure, the guided photonic modes can be extracted with a shorter radiative recombination lifetime; therefore, improve the performance of the devices for VLC. In this paper, we compare various PhC structures with corresponding dynamic behaviors in both small- and large-signal modulation. Faster transient responses and higher efficiency of the out-coupled modes were obtained in the room-temperature time-resolved photoluminescence (TRPL) and Raman scattering measurement. Here, sub-GHz modulation of GaN-based PhCLED is demonstrated, and the PhCLED exhibits a higher bandwidth than the conventional LED structure. Our study also indicates that we can not just keep scaling down the masa size of LEDs to increase the operation frequency owing to the light output power may become dull and reduce the performance of VLC system
Light emitting diodes (LEDs) for visible light communication (VLC) as radio sources is a solution to channel crowding
of radio frequency (RF) signal. However, for the application on high-speed communication, getting higher bandwidth of
LEDs is always the problem which is limited by the spontaneous carrier lifetime in the multiple quantum wells. In this
paper, we proposed GaN-based LEDs accompanied with photonic crystal (PhC) nanostructure for high speed
communication. Using the characteristic of photonic band selection in photonic crystal structure, the guided modes are
modulated by RF signal. The PhC can also provide faster mode extraction. From time resolved photoluminescence (TRPL)
at room temperature, carrier lifetime of both lower- and higher-order modes is shortened. By observing f-3dB -J curve, it
reveals that the bandwidth of PhC LEDs is higher than that of typical LED. The optical - 3-dB bandwidth (f-3dB) can be
achieved up to 240 MHz in the PhC LED (PhCLED). We conclude that the higher operation speed can be obtained due to
faster radiative carrier recombination of extracted guided modes from the PhC nanostructure.
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