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InGaN/GaN multiple quantum well (MQW) diodes perform multiple functions, such as optical emission, modulation and reception. In particular, the partially overlapping spectral region between the electroluminescence (EL) and responsivity spectra of each diode results in each diode being able to sense light from another diode of the same MQW structure. Here, we present a noncontact, optical proximity sensing system by integrating an MQW-based light transmitter and detector into a tiny GaN-on-sapphire chip. Changes in the external environment modulate the light emitted from the transmitter. Reflected light is received by the on-chip MQW detector, wherein the carried external modulation information is converted into electrical signals that can be extracted. The maximum detection proximity is approximately 17 mm, and the displacement detection accuracy is within 1 mm. Based on the detection of distance, we extend the application of the sensor to vibration and pressure detection. This monolithic integration design can replace external discrete light transmitter and detector systems to miniaturize reflective sensor architectures, enabling the development of novel optical sensors.

Nitride-based semiconductor materials inherently have the intriguing functionalities of emission and photodetection. In particular, InGaN/GaN multiple-quantum-well (MQW) diodes exhibit dual light-harvesting and light-emitting modes of operation. Here a multifunctional system is proposed to integrate MQW diodes within a single chip with enhanced functionalities toward diverse applications of the Internet of Things (IoT). When we shine light on the MQW diodes, the absorbed photons can produce electron-hole pairs to charge an external capacitor. The energy of the ambient light is converted into electrical energy, which in turn powers the same MQW diode for lighting. The electrical energy within the capacitor is finally converted into the energy of the emitted light. Therefore, InGaN/GaN MQW diodes can be made to harvest energy from ambient light sources for IoT applications from a self-powered light source to intelligent terminal charging system.

The multiple functionalities of III-nitride semiconductors enable the integration with different components into a multicomponent system with enhanced functions. Here, we propose to fabricate and characterize a monolithic InGaN photonic circuit of a transmitter, waveguide, and receiver on an III-nitride-on-silicon platform. Both the transmitter and the receiver, sharing identical InGaN/GaN multiple-quantum-well structures and fabrication procedures, work to emit light and detect light independently. The 8 μm wide and 200 μm long InGaN waveguide couples the modulated light from the transmitter and sends the guided light to the receiver, leading to the formation of an in-plane light transmission system. The induced photocurrent at the receiver is highly sensitive to the light output of the transmitter. Multi-dimensional light transmissions are experimentally demonstrated at 200 Mb/s. These multifunctional photonic circuits open feasible approaches to the development of III-nitride multicomponent systems with integrated functions for comprehensive applications in the visible region.

We propose, fabricate and demonstrate on-chip photonic integration of suspended InGaN/GaN multiple quantum wells (MQWs) devices on the GaN-on-silicon platform. Both silicon removal and back wafer etching are conducted to obtain membrane-type devices, and suspended waveguides are used for the connection between p-n junction InGaN/GaN MQWs devices. As an in-plane data transmission system, the middle p-n junction InGaN/GaN MQWs device is used as a light emitting diode (LED) to deliver signals by modulating the intensity of the emitted light, and the other two devices act as photodetectors (PDs) to sense the light guided by the suspended waveguide and convert the photons into electrons, achieving 1 × 2 in-plane information transmission via visible light. Correspondingly, the three devices can function as independent PDs to realize multiple receivers for free space visible light communication. Further, the on-chip photonic platform can be used as an active electro-optical sensing system when the middle device acts as a PD and the other two devices serve as LEDs. The experimental results show that the auxiliary LED sources can enhance the amplitude of the induced photocurrent.