Ultrafast 2 × 2 green micro-LED array for optical wireless communication beyond 5 Gbit/s
Journal
Photonics Research
Journal Volume
9
Journal Issue
10
Pages
2077-2087
Date Issued
2021
Author(s)
Abstract
A green 2 × 2 micro light-emitting diode (μ-LED) array with nanostructured grating patterns grown on a semipolar (20-21)-oriented gallium nitride (GaN) buffered layer on (22-43)-oriented sapphire substrate is specially transistor-outline can (TO-can) packaged with a sub-miniature-A (SMA) connector for high-speed data communication beyond 5 Gbit/s. Through a specific design for suppressing the quantum-confined Stark effect (QCSE) in the green 2 × 2 μ-LED array with a low polarization-related electric field and flat quantum well band diagram, the green 2 × 2 μ-LED array exhibits a turn-on voltage of 2.5 V and output power of 0.3 mW at 1 A/cm2. The green 2 × 2 μ-LED array also reveals a wavelength shift from 543 nm to 537 nm smaller than that of conventional devices grown on c-plane buffered GaN substrate due to the inhibited QCSE. The 50 μm emission aperture of the green 2 × 2 μ-LED array ensures a lower capacitance for a larger -3 dB modulation bandwidth, which exhibits -1 dB power compression at a larger bias under high-speed operation, as it is less affected by the high resistance of the single μ-LED element. With a specific TO-can+SMA package, the green 2 × 2 μ-LED array exhibits maximal data rates exceeding 1.5 Gbit/s for the non-return-to-zero on-off keying format and beyond 5.02 Gbit/s for the bit-loaded discrete multitone (BL-DMT) format, which is very promising for optical wireless communication. As the sampling rate increases from 4 GSa/s to 16 GSa/s, the μ-LED array's received signal-tonoise ratio (SNR) improves dramatically from 15.4 dB to 12.2 dB. The SNR remains about 15.4 dB, with a matching bit-error ratio (BER) of 2.7 × 10-3, whereas the 10-fold oversampling of the eight-ray quadrature amplitude modulation orthogonal frequency-division multiplexing (8-QAM OFDM) data stream with 16 GSa/s appears to reduce the SNR by -3 dB, resulting in a decoded BER of 3.3 × 10-3. The green 2 × 2 μ-LED array has demonstrated greater potential in data transmission beyond 5 Gbit/s using the BL-DMT algorithm for future applications in domains of visible light communication or optical wireless communication when packaged with handed mobile devices. ? 2021 Chinese Laser Press.
Subjects
Bandwidth
Capacitance
Electric fields
Gallium nitride
Light emitting diodes
Modulation
Optical communication
Orthogonal frequency division multiplexing
Sapphire
Semiconductor quantum wells
Signal encoding
Signal to noise ratio
Bit error ratios
Discrete multi-tone
Led array
Lightemitting diode
Micro-LED arrays
Optical-wireless communications
Quantum-confined Stark effect
Signal to noise (S/N) ratios
Transistor outlines
Ultra-fast
III-V semiconductors
Type
journal article