InGaN-based red light-emitting diodes: from traditional to micro-LEDs

Zhe Zhuang,Kazuhiro Ohkawa,Daisuke Iida

doi:10.35848/1347-4065/ac1a00

Zhe Zhuang, Kazuhiro Ohkawa + Show 1 more

Open Access

https://doi.org/10.35848/1347-4065/ac1a00

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Abstract

InGaN-based LEDs are efficient light sources in the blue–green light range and have been successfully commercialized in the last decades. Extending their spectral range to the red region causes a significant reduction in LED efficiency. This challenge hinders the integration of red, green, and blue LEDs based on III-nitride materials, especially for full-color micro-LED displays. We review our recent progress on InGaN-based red LEDs with different chip sizes from hundreds to tens of micrometers, including the epitaxial structures, device fabrication, and optical performance (peak wavelength, full-width at half-maximum, light output power, efficiency, temperature stability, and color coordinates).

Highlights

We review our recent progress on InGaN-based red LEDs with different chip sizes from hundreds to tens of micrometers, including the epitaxial structures, device fabrication, and optical performance
III-nitride semiconductors have a direct bandgap and their alloys can cover a wide spectral range from deep UV to near-infrared.1–4) The tremendous success of III-nitride semiconductors is the invention and development of efficient InGaN-based blue/green LEDs,5–7) which have been commercialized for many years and are widely used in illumination and display applications.8–10) To date, violet and blue InGaN-based LEDs have achieved a high wall-plug efficiency (WPE) of 84% and 81%, respectively.11,12) green InGaN-based LEDs for 534 nm emission can reach a peak WPE of 56%.13) These typical values demonstrate that InGaN alloys are an excellent material system for efficient visible light sources
The high operation temperature will cause significant carrier leakage through AlGaInP red LEDs, leading to an obvious efficiency thermal droop.26) when integrating RGB μLEDs, researchers observed mismatched light angular distributions because of the material difference between InGaN blue/green and AlGaInP red μLEDs.27) This mismatched light angular distribution causes a noticeable color shift at different observed angles, which is unfavorable for micro-displays

Summary

Introduction

III-nitride semiconductors have a direct bandgap and their alloys can cover a wide spectral range from deep UV to near-infrared.1–4) The tremendous success of III-nitride semiconductors is the invention and development of efficient InGaN-based blue/green LEDs,5–7) which have been commercialized for many years and are widely used in illumination and display applications.8–10) To date, violet and blue InGaN-based LEDs have achieved a high wall-plug efficiency (WPE) of 84% and 81%, respectively.11,12) green InGaN-based LEDs for 534 nm emission can reach a peak WPE of 56%.13) These typical values demonstrate that InGaN alloys are an excellent material system for efficient visible light sources. The high operation temperature will cause significant carrier leakage through AlGaInP red LEDs, leading to an obvious efficiency thermal droop.26) when integrating RGB μLEDs, researchers observed mismatched light angular distributions because of the material difference between InGaN blue/green and AlGaInP red μLEDs.27) This mismatched light angular distribution causes a noticeable color shift at different observed angles, which is unfavorable for micro-displays. Nanowire or nanocolumn structures are another promising candidate for InGaN-based red LEDs.41) They can neglect the polarization field in InGaN QWs and help to integrate RGB LEDs on the same wafer.42,43) A special InGaN template named InGaN platelets was demonstrated to have relaxed lattice constants, which enabled the shifting of the QW emission from blue to green and red.44) In addition, InGaN QDs presented great potential for red LEDs because they could exhibit improved crystalline quality due to the strain relaxation and suppress the QCSE for InGaN growth with high In composition.). We presented a short conclusive remark about our work and some prospects in InGaN-based red LEDs

InGaN red large-size LEDs

InGaN red μLEDs

EL characteristics of InGaN red μLEDs

Findings

Conclusion and prospect diagrams