Study on the effect of size on InGaN red micro-LEDs

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Physics

Background:

• Micro-light emitting diodes (micro-LEDs) are crucial for advanced display technologies.
• Indium Gallium Nitride (InGaN) is a key material for LEDs, but red InGaN performance is challenging.
• Understanding size-dependent effects in micro-LEDs is vital for optimizing device performance.

Purpose of the Study:

• To investigate the impact of size on the performance of red InGaN micro-LEDs.
• To analyze the wavelength shift and output power density in relation to injection current and die size.
• To explore the potential of red InGaN micro-LEDs for full-color display applications.

Main Methods:

• Fabrication of red InGaN micro-LED dies in five different sizes (100x100 to 10x10 µm²) using laser-based direct writing and maskless technology.
• Characterization of emission wavelength shift and output power density under varying injection currents.
• Analysis of stress release and current density effects on optical properties.

Main Results:

• A notable blue shift in emission wavelength was observed for smaller micro-LEDs as injection current increased (e.g., 10x10 µm² shifted from 617.15 to 576.87 nm).
• This blue shift is attributed to stress release and high current density injection in smaller devices.
• Output power density remained similar for smaller chips at the same current density, differing from AlGaInP micro-LEDs.
• Sidewall defects were effectively passivated, similar to blue micro-LED behavior.

Conclusions:

• Red InGaN micro-LEDs exhibit size-dependent optical characteristics, particularly a blue shift with increasing current in smaller dies.
• The observed phenomena are linked to stress relaxation and high current densities.
• The red InGaN material system shows promise for fabricating full-color displays using GaN-based LED technology.