Phosphor-Based InGaN/GaN White Light-Emitting Diodes With Monolithically Integrated Photodetectors

In this work, we report on the monolithic integrated photodetectors (PDs) in InGaN/GaN light-emitting diodes (LEDs) to monitor the fluctuation of LED intensity over time. The effect of PD position on the light-receiving performance is studied through ray-trace simulation. Three LED-PD devices with different PD positions are fabricated via standard microfabrication processes, and a series of experimental measurements are performed to examine their performances. The design of the PD located in the center of the LED exhibits a 58% increase in the detected photocurrent and has less influence on the emission profile of the LED, compared with the PD formed at the edge. The white light emission is demonstrated by encapsulating the LED-PD device with yellow phosphor and the on-chip PD shows highly similar sensing behaviors as the external Si-based photodiode. Compared with the traditional off-chip detection scheme, the optimal monolithic PD design can provide comparable sensing capabilities, higher compactness, insensitivity to ambient lighting, and less influence on the LED emission profile, making it highly suitable for real-time monitoring of LED intensity variations in various practical and scientific lighting applications.