Optical characterization of GaN-based LED devices through spectroscopic ellipsometry

Abstract

This study analyzes the optical and electrical characteristics of gallium nitride (GaN)-based light-emitting diode (LED) devices, using a dual-rotating compensator spectroscopic ellipsometer. The thickness and optical constants of each layer of a GaN-based LED device were accurately measured, using the appropriate optical models developed in this study. The bandgap energy was estimated by analyzing the absorption spectrum based on the extinction coefficient data. Additionally, the spectroscopic ellipsometry (SE) results were compared with secondary-ion mass spectrometry depth-profile data. The results showed good agreement between the measured and fitted data, confirming the validity of the ellipsometry analysis. Considering the limitations of the existing SE-based techniques such as Cauchy model, Lorentz oscillator model, and effective medium approximations, the significance of this study lies in its pioneering analysis of a complete GaN-based LED device. It demonstrates that SE is a powerful method for nondestructive determination of the key parameters of GaN-based LED devices, providing useful information for improving device performance. This structural and optical analysis is expected to contribute to the advancement of GaN-based optoelectronics.