Monolithic light emitting device and light detecting device fabricated with a commercial LED wafer

Lower cost and smaller volume are imperious demands for active optical measuring and imaging systems. Different from the traditional methods using separate light emitting devices and light detecting devices, a novel way is provided to acquire a simple active optical detecting system. It is found that a commercial light emitting diode (LED) can work as a photodetector utilizing the fact that localized photogenerated carriers within an appropriate p–n junction escape efficiently. Furthermore, a prototype of a simple active optical detecting system is fabricated with a commercial LED wafer on which a light emitting device and a light detecting device are integrated monolithically. It is measured out a good ability in detection for a target with a smooth or rough surface. These results exhibit a considerable possibility of a cheap, flexible and small simple active optical detecting system.