Precise temperature mapping of GaN-based LEDs by quantitative infrared micro-thermography

Area of Science:

• Materials Science
• Optoelectronics
• Thermal Engineering

Background:

• Gallium nitride (GaN)-based light-emitting diodes (LEDs) are crucial for modern lighting and displays.
• Accurate temperature measurement is vital for understanding and improving LED performance and reliability.
• Self-heating effects and temperature gradients can significantly degrade LED efficiency and lifespan.

Purpose of the Study:

• To develop and validate a quantitative infrared micro-thermography method for precise temperature distribution measurement in GaN-based LEDs.
• To identify and correct factors affecting infrared thermography accuracy, such as instrument response, offset radiation, reflected radiation, and surface emissivity.
• To visualize and analyze the spatial distribution of self-heating within LEDs under operational conditions.

Main Methods:

• Quantitative infrared micro-thermography was employed for precise temperature mapping.
• Calibration was performed using a black-painted dummy wafer under identical conditions to minimize errors.
• Correction factors for non-uniform instrument response, offset radiation, reflected radiation, and emissivity were determined and applied.

Main Results:

• A precise absolute temperature image of biased LEDs was successfully obtained after correcting for measurement inaccuracies.
• The study identified localized self-heating emerging near the p-contact edge of the LED surface.
• A significant temperature gradient was observed at high injection levels, attributed to current crowding.

Conclusions:

• The developed infrared micro-thermography method enables accurate measurement of temperature distribution in GaN-based LEDs.
• Localized self-heating and temperature gradients near the p-contact edge are critical factors impacting LED performance and reliability.
• Understanding these thermal phenomena is essential for optimizing GaN-based LED design and operation.