Improvement in quantum efficiency of green GaN-based micro-LED by trapezoidal quantum well

The main challenges in the application of GaN-based full-color micro-light-emitting diodes (micro-LEDs) are size-dependent effects and low quantum efficiency, especially for green micro-LEDs. In this study, we propose to use a trapezoidal quantum well (QW) structure in GaN-based green micro-LEDs. The trapezoidal QW structure is able to improve the electron hole wave function overlap, thus increasing the external quantum efficiency (EQE). Green micro-LEDs with active region size of 75 × 64 μm2 are fabricated by metal organic chemical vapor deposition. The peak EQE of the green trapezoidal QW micro-LED reaches 15.8% at a low injection current density of 0.6A/cm2, which is 1.96 times higher than that of conventional rectangular QW. The test results indicate that the trapezoidal QW structure greatly improves the quantum efficiency of green micro-LED, inhibits the blue shift of peak wavelength and improves color purity, which paves the way to single substrate full-color micro-LED display with high-performance. The technology proposed in this paper does not change the production line equipment, but improves the traditional process, so it is expected to significantly improve the external quantum efficiency of the existing green micro-LED under the existing equipment. The production technology of existing InGaN QW micro-LED is directly adopted, and the EQE can be further improved if some new dry etching and passivation methods are applied. •Due to the quantum-confined Stark effect, the electron and hole wave functions are separated in space.•Based on the quantum well energy band model, a trapezoidal quantum well structure is designed.•Using a trapezoidal quantum well structure in GaN-based green micro-LEDs.•The trapezoidal QW structure greatly improves the quantum efficiency of green micro-LED; inhibits the blue shift of peak wavelength.