Pulse-Modulation Controllable Monolithic Full-Color Semipolar GaN-based Light Emitting Diodes

Monolithic multi-color light-emitting diodes (LEDs) offer numerous advantages as multi-functional lighting sources. However, the achievement of full-color monolithic LEDs spanning from red to blue wavelengths is limited by the InN-GaN material system. To overcome this limitation, this work demonstrates a new approach using hexagonal epitaxial lateral overgrowth to reduce the density of crystal defects and form micro-surface structures. By utilizing arrowhead-like surfaces in semipolar GaN films, indium incorporation can be controlled, leading to larger band-filling effects and enabling full-color red, green, and blue emissions from a single LED. Nonetheless, the red emission in monolithic full-color LEDs is weaker than the blue emission due to the band-filling induced blueshift that occurs with increasing current injection. To address this issue, pulse amplitude modulation and pulse width modulation modes are introduced to control the emission intensity from red to blue wavelengths. As a result, the study achieves a monolithic trichromatic white LED with color coordinates of (0.2985, 0.3948) and a color temperature of & AP;6700 K by simultaneously emitting red, green, and blue LEDs with the same emission intensities. This achievement holds great promise for the development of high-performance full-color LEDs for multifunctional lighting sources that can span red, green, and blue wavelengths.