Highly efficient InGaN green mini-size flip-chip light-emitting diodes with AlGaN insertion layer

Area of Science:

• Solid State Physics
• Materials Science
• Optoelectronics

Background:

• Indium gallium nitride (InGaN) based mini light-emitting diodes (mLEDs) are crucial for display technologies.
• Defect formation, particularly 'V' defects in InGaN/GaN multiple quantum wells (MQWs), limits device performance and efficiency.
• Optimizing the material quality and device architecture is essential for high-performance mLEDs.

Purpose of the Study:

• To investigate the impact of an aluminum gallium nitride (AlGaN) insertion layer on the performance of InGaN-based mLEDs.
• To reduce 'V' defects within the active region of mLEDs and enhance radiative recombination efficiency.
• To achieve high-efficiency green mLEDs suitable for advanced display applications.

Main Methods:

• Metal organic chemical vapor deposition (MOCVD) was employed to fabricate InGaN/GaN MQWs with an AlGaN insertion layer.
• High-resolution transmission electron microscopy (HRTEM) was used to analyze the material structure and defect evolution.
• Photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopy were utilized to assess radiative recombination efficiency.

Main Results:

• The AlGaN insertion layer effectively suppressed the formation of 'V' defects in the InGaN/GaN MQWs.
• PL and TRPL measurements showed a significant increase in radiative recombination efficiency.
• Fabricated 523 nm green flip-chip mLEDs (0.025 mm²) with a distributed Bragg reflector (DBR) achieved a high external quantum efficiency (EQE) of 38.0% and a wall-plug efficiency (WPE) of 32.1% at 20 A cm^-2.
• A low forward voltage of 2.8 V was recorded at the working current density.

Conclusions:

• The integration of an AlGaN insertion layer is a highly effective strategy for mitigating 'V' defects in InGaN/GaN MQWs.
• This approach significantly enhances the radiative efficiency of InGaN-based mLEDs.
• The demonstrated high-performance green mLEDs show great promise for next-generation display applications.