Monolithically integrated voltage-controlled MOSFET-LED device based on a GaN-on-silicon LED epitaxial wafer.

We report a novel monolithically integrated voltage-controlled metal-oxide-semiconductor field effect transistor (MOSFET)-LED device based on a GaN-on-silicon LED epitaxial wafer. An N-channel enhancement mode MOSFET and an InGaN/GaN multiple-quantum-well (MQW) thin-film LED featured with a suspended membrane are in series connection to constitute the monolithically integrated device without external metal interconnection. A recessed gate structure and AlGaN channel are innovatively adopted to realize an enhancement mode transistor. The fabrication of the MOSFET-LED includes no additional ion implantation or epitaxial growth compared with that of a common MQW LED, which greatly simplifies the device structure and production processes. The measured turn-on voltage of the LED is approximately 4 V, and the threshold voltage of the MOSFET is extrapolated as 5.2 V. The results demonstrate relatively good dimming and switching capacities of the integrated MOSFET-LED. This integration scheme also has potential to achieve a large-scale optoelectronic integrated circuit.

Simultaneous transmission, detection, and energy harvesting.

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 SiO2/TiO2 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.

Asymmetric optical links using monolithic III-nitride diodes.

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.