Hybrid GaN LED with capillary-bonded II–VI MQW color-converting membrane for visible light communications

Abstract

The rapid emergence of gallium-nitride (GaN) light-emitting diodes (LEDs) for solid-state lighting has created a timely opportunity for optical communications using visible light. One important challenge to address this opportunity is to extend the wavelength coverage of GaN LEDs without compromising their modulation properties. Here, a hybrid source for emission at 540 nm consisting of a 450 nm GaN micro-sized LED (micro-LED) with a micron-thick ZnCdSe/ZnCdMgSe multi-quantum-well color-converting membrane is reported. The membrane is liquid-capillary-bonded directly onto the sapphire window of the micro-LED for full hybridization. At an injection current of 100 mA, the color-converted power was found to be 37 μW. At this same current, the −3 dB optical modulation bandwidth of the bare GaN and hybrid micro-LEDs were 79 and 51 MHz, respectively. The intrinsic bandwidth of the color-converting membrane was found to be power-density independent over the range of the micro-LED operation at 145 MHz, which corresponds to a mean carrier lifetime of 1.9 ns.

Visible light communication using InGaN optical sources with AlInGaP nanomembrane down-converters

“…A long-pass filter (550 nm cutoff wavelength) was placed before the receiver for measurements of the down-converted light. The modulation bandwidth was extracted from the detected modulation amplitude versus frequency as detailed in [8,9]. The optical spectra were recorded with an Ocean Optics USB4000 Fiber Optic Spectrometer (2.5 nm resolution).…”

“…The current dependence can be attributed to the reduced carrier lifetime in the active region of the micro-LEDs as the current, and hence the carrier density, increases [12,21]. The response of the NM, obtained by subtracting the standalone micro-LED response to the response of the hybrid device [9], further affects the bandwidth of the hybrid sources. The intrinsic response of the NM is between 130 MHz and 320 MHz, which is at least two order of magnitude faster than conventional phosphors [22].…”

“…However, phosphors respond slowly to modulated light, which is not ideal for VLC. Other color-converting materials are therefore being researched for VLC including organic semiconductors [6,7], colloidal nanocrystals [8] and inorganic semiconductor epilayers [9]. The latter offers an all-inorganic, photostable solution to color-conversion, which is particularly attractive for high power applications.…”

“…Recently, we have demonstrated a hybrid green-emitting LED based on a II-VI multiquantum well (MQW) epilayer structure a couple of micron-thick for color-conversion of a blue micro-LED [9]. Other groups had previously shown similar heterogeneous hybridization of epitaxial structures as a way to push the emission of GaN LEDs to longer wavelengths [10,11].…”

Micro Light‐Emitting Diodes for Display and Flexible Biomedical Applications

“…On the other hand, OLED presented screen burn‐in and short life span of four years due to the thermal/humid instability of organic materials. In addition, µLEDs have great potentials to produce high‐quality images because of their fast response time (≈5 × 10 4 times shorter than that of OLEDs), high color reproduction rate of 140%, and wide view angle . At identical pixel number and light intensity, the power efficiency of a µLED display was 77 and 4 times higher than those of LCD and OLED displays, respectively .…”