Color tunable inverted pyramid micro-LEDs based on nano-patterned sapphire substrates.

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Micro-scale light-emitting diodes (Micro-LEDs) offer a pathway to simple, low-cost full-color displays.
• Achieving color tunability and high performance in Micro-LEDs is crucial for advanced display and communication technologies.

Purpose of the Study:

• To demonstrate the growth of 3D inverted pyramid Gallium Nitride (GaN) on nano-patterned sapphire substrates (NPSS) for Micro-LED fabrication.
• To investigate the color-tunability and modulation bandwidth of these Micro-LEDs for potential applications in the Internet of Everything (IoE).

Main Methods:

• Growth of 3D inverted pyramid GaN structures on NPSS using a sputtered Aluminum Nitride (AlN) nucleation layer.
• Epitaxial growth and fabrication of Micro-LED devices (20-100 µm) on the inverted pyramid structures.
• Electroluminescence (EL) and modulation bandwidth measurements across varying current densities.

Main Results:

• Improved uniformity of inverted pyramids using sputtered AlN nucleation layer.
• Significant color tunability observed, with electroluminescence (EL) wavelength shifting from 660 nm to 470 nm as current increases, covering 97% of the sRGB color gamut.
• Observation of different modulation bandwidths for polar and semipolar Indium Gallium Nitride (InGaN) multi-quantum-well (MQW) facets, with a highest -3 dB electro-optic bandwidth of 1.28 GHz achieved.

Conclusions:

• 3D inverted pyramid GaN Micro-LEDs on NPSS enable wide color-tunable displays.
• The distinct carrier recombination rates in polar and semipolar InGaN MQW facets influence modulation bandwidths.
• These Micro-LEDs show promise for integrated display and communication functionalities in the IoE era.