Monolithically Integrated GaN LED/Quasi-Vertical Power U-Shaped Trench-Gate MOSFET Pairs Using Selective Epi Removal

We report on the demonstration of monolithically integrated light-emitting diode (LED) and quasi-vertical U-shaped trench-gate metal-oxide-semiconductor field-effect transistor (UMOSFET) in GaN. Selective epi removal (SER) approach was used on an LED-on-FET epi stack on sapphire substrates. Individual p-GaN layers were used for LED and FET in our design. LED light modulation by the supply voltage and the FET gate voltage was realized, and an integrated $350\mu \text {m}\times {350}\mu \text{m}$ LED/UMOSFET pair exhibits a light output power (LOP) of 4.9 W/cm ² or 6.0 mW. An integrated device with a UMOSFET driving a 3-LED chain was also demonstrated. The normally-off power UMOSFET has a threshold voltage of 7 V, a breakdown voltage of 208 V, and a specific on-resistance of 23 $\text{m}\Omega $ -cm ² , in which hexagonal cells were applied to obtain identical m-plane MOS gate interfaces. The effect of FET sizing on integrated pairs was also studied, and a trade-off model of FET/LED power ratio vs. FET/LED area ratio was created, which serves as universal criterion for FET/LED integration. The tested device with the best trade-off has FET/LED area ratio of 24% and FET/LED power ratio of 56%. This work creates a new building block for future GaN light-emitting integrated circuits (LEICs).