Monolithic III-nitride photonic circuit for multifunctional visible light communication

Nitride semiconductor materials inherently have the intriguing functionalities of simultaneous emission, transmission and photodetection, which enable the photonic integration of emitter, waveguide, modulator and photodiode on a single chip [1-3]. In particular, InGaN/GaN multiple-quantum-well (MQW) diodes exhibit a simultaneous light-emitting light-detecting function, endowing the MQW-diode with the capability of producing transmitter and receiver using same fabrication procedure for visible light communication. Both transmitter and receiver share the identical InGaN/GaN MQW active region. To validate the device concept, we propose a wafer-level procedure for the fabrication of monolithic III-nitride photonic circuit on an III-nitride-on-silicon platform for multifunctional visible light communication. Epitaxial films are grown on (111) silicon substrates with intermediate Al-composition step-graded buffer layers, and membrane-type monolithic III-nitride photonic circuit is obtained by a combination of silicon removal and III-nitride film backside thinning. Monolithic III-nitride photonic circuit of emitter, waveguide and photodiode forms an in-plane visible light communication system [4], and the out-of-plane light emission is used for building a free-space visible light communication system [5]. The III-nitride photonic circuit experimentally demonstrates a data transmission over 100 Mb/s on a wire-bonded chip. Moreover, a full-duplex light communication is demonstrated by utilizing simultaneous light-emitting light-detecting function of the MQW-diode, and the self-interference cancellation method is used to decode the superimposed signals. These results are promising for the development of monolithic III-nitride photonic circuit for diverse applications in visible light communication, optical sensor and intelligent displays.