Monolithic Integration of GaN-Based Green Micro-LED and Quasi-Vertical MOSFET Utilizing a Hybrid Tunnel Junction

We demonstrated the monolithic integration of GaN-based driving metal-oxide-semiconductor field effect transistor (MOSFET) on micro-light-emitting diodes ( $\mu $ LEDs) by regrowing a hybrid tunnel junction (TJ) on top of a commercial green LED wafer. The hybrid TJ served not only as the current spreading layer for $\mu $ LEDs, but the n/p/n structure of the LED + TJ stack could also be utilized for fabricating a quasi-vertical driving MOSFET. The $\mu $ LED was connected to the MOSFET via the conductive n-GaN layer. By modulating the gate supply voltage, the MOSFET effectively controlled the injection current of the $\mu $ LED, allowing for precise modulation of its output performance. The integrated 60- $\mu \text{m}~\mu $ LED exhibited a high output power of 0.12 mW (~4.2 W/cm ² ) at a current of 0.3 mA (around 10 A/cm ² ) when the MOSFET was modulated with $\text{V}_{\text {DD}}$ = 5 V and $\text{V}_{\text {G}}$ = 16 V, demonstrating good $\mu $ LED performance and comparable driving capability to previous GaN-based MOSFETs and oxide-based thin film transistors. This work provides a new method for GaN FET/LED monolithic integration, which paves the way for potential applications in visible light communication and flexible $\mu $ LED displays.