The InGaN/GaN multiple-quantum-well (MQW) diode has selectable functionalities with emission and detection in the visible region due to the MQW-based p-n junction structure, which is employed to achieve on-chip optocoupling. Here, we propose to fabricate a suspended InGaN/GaN MQW diode on an III-nitride-on-silicon platform by a combination of silicon removal and III-nitride backside etching. Spatial simultaneous light-emitting light-detecting functionality, in which the detected light comes from an external light source, is experimentally demonstrated, endowing the MQW diode with the capability of contributing to intelligent displays as well as full-duplex visible light communication. As a transmitter, the InGaN/GaN MQW diode demonstrates out-of-plane data transmission at 120 Mb/s using visible light.