Infrared Micro Thermography of High-Power AlInGaN LEDs Using High Emissivity (black) Coating in IR and Transparent in the Visible Spectral Region

Abstract

We report a technique which can simplify and improve the Infrared (IR) micro-thermography of light-emitting diodes (LEDs) by the use of a special thin-film coating which combines strong absorption in the wavelength range of sensitivity of IR microscope (2.5-3µm) and transparency in the visible region of the own LED radiation. As is well known, conventional IR temperature measurements, made on the LEDs, lead to significant difficulties and errors as consequence of the optical transparency of substrate/heterostructure layers and low emissivity of metalized contacts. The proposed method allows avoiding the time-consuming procedure of emissivity calibration for different materials forming LEDs, while increasing the measurement accuracy.

Junction Temperature Optical Sensing Techniques for Power Switching Semiconductors: A Review

“…The uncertainties of local temperature due to variation in surface emissivity are due to changes in radiative recombination properties of semiconductor layers, bonding elements, and coating having different transparency or reflectance properties to infrared radiation, making it difficult to determine the surface emissivity accurately. These issues have been mitigated in the literature with high emissivity coatings [50,76]. Another alternative to obtain an accurate measurement of emitted radiation from a target is to place micro carbon particles near the targeted surface, eliminating the need for coating [77].…”