Advancing Long-Wavelength InGaN Micro-LEDs as Wavelength-Selective Detectors for White-Light Communication

Abstract

Long-wavelength InGaN-based microlight emitting diodes (μLEDs) have the potential for novel display and visible light communication (VLC). In this study, red and yellow μLEDs were fabricated for VLC applications as VLC transmitters and photodiodes (PDs). Stress modulation engineering and atomic layer deposition (ALD) techniques were employed to improve the transmission and detection performance. When operating as VLC transmitters, the red and yellow μLEDs exhibits high modulation bandwidth of 439.7 and 532.5 MHz at 2000 A/cm2, achieving a data rate of 1.9 and 2.4 Gbps, respectively. When operating as VLC PDs, long-wavelength emitting μLEDs with high indium component QW exhibit longer wavelength absorption edge, which is expected to achieve higher responsivity to blue light while filtering out the fluorescence component. The response spectra of the red and yellow μLED PDs overlap a large portion of the blue signal. The red and yellow μLEDs achieved responsivities of up to 0.208 and 0.135 A/W, respectively, for 450 nm light, higher than those of the reported InGaN LED-based photodetectors. In addition, owing to the wavelength selectivity, the long-wavelength μLED PDs could filter the slow fluorescence emission, thus achieving white light modulation bandwidth several times that achieved by adopting a silicon-based detector. A white-light VLC system was experimentally demonstrated. Maximum transmission rates of 1.2 and 1.05 Gbps were achieved based on red and yellow μLEDs operating as PDs, respectively. The findings of this study indicate that employing red μLED pixels as wavelength-selective PDs in future μLED information displays is an effective strategy for phosphor-based white-light communication.