In this Letter, we experimentally achieve high-speed ultraviolet-C (UVC) communication based on a 276.8 nm UVC micro-LED. A record
−
3
d
B
optical bandwidth of 452.53 MHz and light output power of 0.854 mW at a current density of
400
A
/
c
m
2
are obtained with a chip size of 100 µm. A UVC link over 0.5 m with a data rate of 2 Gbps is achieved using 16-ary quadrature amplitude modulation orthogonal frequency division multiplexing and pre-equalization, and an extended distance over 3 m with a data rate of 0.82 Gbps is also presented. The demonstrated high-speed performance shows that micro-LEDs have great potential in the field of UVC communication.
GaN green LEDs grown on the Si substrate are expected
to become
low-cost and high-efficiency green light sources in future years,
thus promoting the potential of GaN-on-Si green micro-LEDs for display
and visible light communication (VLC), but the performances of the
GaN-on-Si green micro-LEDs have yet to be fully investigated. In terms
of display, a nondestructive transfer printing process is adopted
and the characteristics of GaN-on-Si green micro-LEDs before and after
being transferred to the glass substrate are presented in this work.
The removal of the Si substrate causes almost no electrical damage
to the device, and at a low current density of 1 A/cm2,
the EQE of the micro-LED can be doubled and the device can still maintain
good color purity. In terms of VLC, a −3 dB bandwidth up to
613 MHz has been achieved for 80 μm micro-LED under the current
density of 2 kA/cm2, and a data rate of 4.65 Gbps is obtained.
These results indicate that GaN-on-Si green micro-LEDs have great
application prospects in both display and communication fields.
In this Letter, high-speed optical wireless communication (OWC) with three light-emitting diodes (LED) and five micro-LEDs (μLEDs) is proposed as a proof-of-concept wavelength division multiplexing (WDM) system. It covers a wide spectrum from deep ultraviolet (UV) to visible light and thus could offer both visible light communication (VLC) and UV communication simultaneously. An aggregated data rate of up to 25.20 Gbps over 25 cm free space is achieved, which, to the best of our knowledge, is the highest data rate for LED-based OWC ever reported. Among them, the five μLEDs offer a data rate of up to 18.43 Gbps, which, to the best of our knowledge, is the highest data rate for μLED-based OWC so far. It shows the superiority and potential of μLEDs for WDM-OWC. Additionally, a data rate of 20.11 Gbps for VLC is achieved.
UV-C LEDs have great application prospects in the fields of sterilization, disinfection, and non-line-of-sight solar-blind communication. However, the efficiency is not high enough to satisfy the applications and needs to be improved. In this work, AlGaN based UV-C LEDs (273 nm) with size from 8 to 200 μm were fabricated to evaluate the size effect of external quantum efficiency (EQE). Higher EQE was detected in smaller-size UV-C micro-LEDs. Simulations on EQE were performed. The analysis on experimental data and the simulation results reveals that higher EQE originates from both higher internal quantum efficiency (IQE) at high current densities due to better current spreading and higher light extraction efficiency (LEE) due to larger proportion of the sidewall. From the efficiency improvement mechanism, it is concluded that the severer current density non-uniformity and LEE loss of UV-C devices compared with visible or near ultraviolet LEDs can be effectively restrained by preparing micro-LEDs. Our work helps to optimize the efficiency characteristics for UV-C applications.
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