InGaN/GaN superlattice underlayer for fabricating of red nanocolumnμ-LEDs with (10-11) plane InGaN/AlGaN MQWs

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Indium gallium nitride (InGaN) nanostructures are key for light-emitting diodes (LEDs).
• Controlling crystal plane orientation is vital for optimizing LED efficiency and color output.
• Previous research has focused on c-plane growth, limiting performance for certain wavelengths.

Purpose of the Study:

• Investigate the growth behavior of InGaN-based nanocolumn arrays.
• Fabricate red-emitting nanocolumn micro-light emitting diodes (μ-LEDs).
• Understand the role of superlattice structure on crystal plane formation and LED performance.

Main Methods:

• Utilized scanning transmission electron microscopy (STEM) to analyze the internal structure of InGaN/GaN superlattice (SL) layers.
• Varied the number of SL pairs to study its effect on nanocolumn crystal plane evolution.
• Fabricated red nanocolumn μ-LEDs using optimized InGaN/AlGaN multiple-quantum-well (MQW) structures grown on semipolar planes.

Main Results:

• Observed a transition from c-plane to semipolar (10-11) plane at the nanocolumn top with increasing SL pairs (15-20 pairs).
• Confirmed uniform SL layer growth and stable (10-11) plane formation.
• Demonstrated growth of semipolar InGaN active layers on the (10-11) plane SL underlayer.
• Achieved a red nanocolumn μ-LED with a 12 μm emission window, yielding an external quantum efficiency of 1.01% at 51 A cm⁻².
• Developed a process for μ-LEDs with smaller emission windows (5 μm) using a flat p-GaN contact layer.

Conclusions:

• The formation of a semipolar (10-11) plane in InGaN/GaN SLs is critical for achieving efficient red emission in nanocolumn μ-LEDs.
• Optimized SL growth conditions enable controlled fabrication of nanocolumn μ-LEDs with desired crystal orientations.
• The developed fabrication process is suitable for producing high-performance μ-LEDs with small emission windows.