Spectrally stable red c-plane InGaN-based LEDs enabled by composition-graded AlGaN barriers.

Area of Science:

• Optoelectronics
• Materials Science
• Solid State Physics

Background:

• Red-emitting InGaN LEDs are essential for micro-displays and visible light communication (VLC).
• Internal polarization fields and quantum-confined Stark effect (QCSE) limit their performance.
• Existing red InGaN LEDs suffer from spectral instability and efficiency droop.

Purpose of the Study:

• To improve the luminescence performance of red InGaN LEDs.
• To alleviate internal polarization fields and suppress QCSE.
• To achieve high spectral stability and reduce efficiency droop.

Main Methods:

• Fabrication of red InGaN LEDs with a graded Al content AlGaN barrier structure.
• Comparison with LEDs featuring a constant Al content AlGaN barrier.
• Characterization using photoluminescence (PL) and time-resolved photoluminescence (TRPL).

Main Results:

• Graded AlGaN barriers effectively alleviate internal polarization fields and suppress QCSE.
• Red LEDs with graded barriers show high spectral stability, maintaining a constant emission wavelength (620 nm) across various drive currents.
• TRPL measurements indicate enhanced electron-hole overlap and faster radiative recombination in graded structures.
• Improved quantum efficiency and reduced efficiency droop were observed.

Conclusions:

• A graded Al content AlGaN barrier is a practical approach to overcome polarization-induced limitations in III-nitride optoelectronics.
• This method significantly enhances the performance of red InGaN LEDs.
• The findings have major implications for micro-LED displays needing color uniformity and VLC systems requiring stable, high-speed light sources.