Monolithically and Vertically Integrated LED-on-FET Device Based on a Novel GaN Epitaxial Structure

Optoelectronic devices, such as light-emitting diodes (LEDs), based on GaN-based semiconductor compounds are widely used for their advantages of long life, high reliability, and low energy consumption. The persistent challenge is integrating LED with transistors to achieve smaller size, lighter weight, higher speed, and more reliable optoelectronic integrated circuits. Here, we report monolithically and vertically integrated LED-on-FET devices fabricated on a novel GaN epitaxial structure. The designed device structure and fabrication process are simple. It also eliminates the extra area occupied by the transistor, and the shared n-GaN layer between the LED and FET reduces interconnect resistance and improves reliability. The measured threshold voltage ( ${V}_{\text {Th}}$ ) of the LED-on-FET device is extrapolated as 3.9 V at the voltage ( ${V}_{\text {DD}}$ ) of 5 V, and ${V}_{\text {Th}}$ decreases with the increase of ${V}_{\text {DD}}$ . More importantly, the gate voltage ( ${V}_{\text {GS}}$ ) shows good performance in modulated electroluminescence (EL) intensity and switching capability of the LED. The integrated LED efficiently emits light modulation with a wavelength of 440 nm at ${V}_{\text {DD}}$ = 9 V and ${V}_{\textit {GS}}$ = 4–9 V (step = 1 V), which are necessary for devices in applications, such as displays and smart lighting. This epitaxy structure and integration scheme is promising in achieving large-scale optoelectronic integrated circuits, such as the next-generation micro-LED and nano-LED with super compact integrated drivers.