Ambient Temperature–Corrected Mechanical Stress Mapping of Gallium Nitride and Aluminum Indium Gallium Phosphide Films by Raman Scattering Spectroscopy for Characterization of Light-Emitting Diodes

摘要

Raman spectroscopy can provide a detailed analysis of mechanical stress in crystalline materials through the measurement of shifts in vibrational frequency. However, the ambient temperature drift during measurements can lead to inaccurate mechanical stress values. Herein, the 2D Raman mapping analysis of gallium nitride (GaN) and aluminum indium gallium phosphide (AlInGaP) epitaxial films within packaged light-emitting diode (LED) devices reveals micrometer-scale localized stress distributions. A temperature-corrected measurement method is developed to evaluate the mechanical stress of InGaN LED dies at various LED operating conditions. The impact of die design on mechanical stress is studied for both GaN on Al_2O_3 (chip scale package, CSP) and GaN thin-film flip chip (TFFC) designs. Raman mapping of AlInGaP LEDs is also demonstrated and shows comparable resolution with the GaN LED results.