Multiple-quantum well (MQW) III-nitride diodes can both emit and detect light. In particular, a III-nitride diode can absorb shorter-wavelength photons generated from another III-nitride diode that shares an identical MQW structure because of the spectral overlap between the emission and detection spectra of the III-nitride diode, which establishes a wireless visible light communication system using two identical III-nitride diodes. Moreover, a wireless light communication system using a modulating retro-reflector (MRR) enables asymmetric optical links, which forms a two-way optical link using a single transmitter and receiver. Here, in association with an MRR, we propose, fabricate, and characterize asymmetric optical links using monolithic III-nitride diodes, where one III-nitride diode functions as a transmitter to emit light, an MRR reflects light with the encoded information, another monolithically integrated III-nitride diode serves as a receiver to absorb the reflected light to convert optical signals into electrical ones, and the encoded information is finally decoded. Advanced monolithic III-nitride asymmetric optical links can be developed toward Internet of Things (IoT) deployment based on such multifunction devices.
Multifunctioning InGaN/GaN multi‐quantum well (MQW) diodes can transmit and detect light separately. In particular, MQW diodes have spectral overlap between electroluminescence (EL) and responsivity, conferring the unique ability to detect light emitted by another device sharing an identical MQW structure. Herein, a III‐nitride transmitter and a receiver on a single chip are monolithically integrated, which can establish an asymmetric optical link and significantly reduce material and processing costs. By attaching the chip to the skin with the transmitter emitting toward it, the device can monitor cardiac activity. Heart pulses change blood volume of the vascular bed, which modulates the reflected light. The receiver absorbs that light and converts it into electrical signals. Finally, by integrating a programmed circuit, the biological signals are analyzed. Herein, a feasible approach to monitor heart rate and cardiac‐related pulse information simultaneously is provided.
Due to the electro-optic property of InGaN multiple quantum wells, a III-nitride diode can provide light transmission, photo detection, and energy harvesting under different bias conditions. Made of III-nitride diodes arrayed in a single chip, the combination allows the diodes to transmit, detect, and harvest visible light at the same time. Here, we monolithically integrate a III-nitride transmitter, receiver, and energy harvester using a compatible foundry process. By adopting a bottom
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distributed Bragg reflector, we present a III-nitride diode with a peak external quantum efficiency of 50.65% at a forward voltage of 2.6 V for light emission, a power conversion efficiency of 6.68% for energy harvesting, and a peak external quantum efficiency of 50.9% at a wavelength of 388 nm for photon detection. The energy harvester generates electricity from ambient light to directly turn the transmitter on. By integrating a circuit, the electrical signals generated by the receiver pulse the emitted light to relay information. The multifunctioning system can continuously operate without an external power supply. Our work opens up a promising approach to develop multicomponent systems with new interactive functions and multitasking devices, due to III-nitride diode arrays that can simultaneously transmit, detect, and harvest light.
Visible light communication (VLC) is a key technology for 6G. Here, we propose, fabricate, and characterize a vertical-structure light-emitting diode (VSLED) to manage the dilemma of both power and speed for VLCs. Ultrathin VSLED architecture offers the unique features of decreasing the RC time constant for increasing modulation bandwidth and reducing confined optical modes inside the diode for enhancing light extraction. A 580-nm-thick VSLED with a dominant emission wavelength of 427.8 nm is implemented on a 2-in. metal-based bonded III-nitride-on-silicon wafer. Based on a bit-loading discrete multitone modulation scheme, we establish a visible light communication system using 1 × 1 mm2 VSLED, which can achieve a data transmission rate of 608 Mbps at a baud rate of 200 MBaud.
Both energy and information are different manifestations of light. Using light to offer the coexistence of sensing, communication, and energy harvesting functionalities, monolithically integrated III‐nitride diode system toward the Internet of Things is dealt with. The III‐nitride receiver is capable to convert optical signals into electronic ones and forward them to the transmitter. The energy harvester generates electricity from light to turn on the transmitter, which, in turn, can transmit information optically to other proximally located devices for analysis or relay the data over longer distances. This monolithic III‐nitride optoelectronic system can simultaneously achieve wireless energy harvesting and communication through light. The truly self‐powered, integrated III‐nitride system is a paradigm change where the previously competing sensing, communication, and energy harvesting operations can be jointly implemented on a single chip.
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