Monolithically Integrating GaN MicroLEDs on HEMTs With a New Approach for Lower On-Resistance

High-electron-mobility transistors (HEMTs)-driven microLEDs have been reported a lot for voltage-controllable light emission used for visible light communication, micro-display, and biosensing, etc. Existing integration approaches are based on an n-GaN/2DEG interconnection scheme using the selective area growth approach. Due to the limited area of interconnection interface between microLEDs and HEMTs, and poor quality of selectively overgrown epitaxy resulting from etching damages to HEMT buffer surfaces, integrated devices have relatively large on-resistance and poor current spreading. This paper proposes a new approach to integrating HEMTs with microLEDs. Without etching down HEMT to buffer for selective area growth, the microLEDs are selectively overgrown on top of AlGaN/GaN HEMT surface directly. This both avoids causing etching damages to the regrowth interface prior to microLED overgrowth and enables the interconnection interfaces to be expanded greatly to the whole bottom surfaces of n-GaN of microLEDs. The integrated HEMT-microLED device adopting such an integration scheme demonstrates a much smaller on-resistance, largely reducing power consumption.