A discrete core-shell-like micro-light-emitting diode array grown on sapphire nano-membranes

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Micro-light-emitting diodes (micro-LEDs) are crucial for next-generation displays, but their fabrication often involves plasma etching, which can damage devices.
• Achieving high efficiency and low defect density in micro-LEDs is challenging due to material limitations and fabrication processes.

Purpose of the Study:

• To develop a plasma-etching-free fabrication method for discrete micro-LED arrays.
• To investigate the use of sapphire nano-membranes as compliant substrates for micro-LED growth.
• To evaluate the impact of compliant substrates on crystal quality, efficiency, and optical properties of micro-LEDs.

Main Methods:

• Growing discrete core-shell-like micro-LED arrays on 100 nm-thick sapphire nano-membrane arrays.
• Utilizing the compliant nature of sapphire nano-membranes to reduce threading dislocation density.
• Characterizing the micro-LEDs using photoluminescence and cathodoluminescence spectroscopy.

Main Results:

• Successfully fabricated multi-faceted micro-LEDs (4 μm × 16 μm) without plasma etching.
• Reduced threading dislocation density by 59.6% compared to planar substrates.
• Achieved a 44% enhancement in internal quantum efficiency and 3.3 times higher photoluminescence intensity.
• Observed core-shell-like multiple quantum wells (MQWs) on all facets, potentially reducing non-radiative recombination.

Conclusions:

• Sapphire nano-membrane arrays provide a viable, compliant substrate for high-quality micro-LED growth.
• This approach offers an attractive, plasma-etching-free platform for fabricating efficient micro-LEDs.
• The core-shell MQW structure shows promise for mitigating surface recombination and leakage currents.