Enhanced light-extraction efficiency and emission directivity in compact photonic-crystal based AlGaInP thin-films...

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• AlGaInP/InGaP multiple quantum well (MQW) structures are key for color conversion in displays.
• Efficient light extraction is crucial for improving display brightness and performance.
• Photonic crystals offer a promising route to control light emission from semiconductor devices.

Purpose of the Study:

• To investigate the use of photonic crystals with varying opto-geometrical parameters for enhanced light extraction from AlGaInP/InGaP MQW color converters.
• To demonstrate blue-to-red and green-to-red color conversions using photonic crystal structures.
• To provide design guidelines for optimizing light extraction in MQW color converters.

Main Methods:

• Fabrication and characterization of AlGaInP/InGaP MQW structures patterned with photonic crystals.
• Room-temperature photoluminescence measurements with 405nm and 514nm excitation wavelengths.
• Analysis using 3D-Finite-Difference Time-Domain (3D-FDTD) simulations and a phenomenological model based on coupled-mode theory.

Main Results:

• Demonstrated efficient, compact, and highly directional light extraction from MQW color converters.
• Achieved up to ~8 times higher light extraction gains compared to unpatterned structures.
• Identified optimal photonic crystal designs (e.g., 400nm lattice period square nanopillars) for short extraction lengths and directional emission.

Conclusions:

• Photonic crystals significantly enhance light extraction efficiency in AlGaInP/InGaP MQW color converters.
• The developed design guidelines are crucial for realizing high-performance color converters.
• This work paves the way for single-wafer, full-color microdisplays using inorganic MQW epi-layers.