Research on contactless electroluminescence for micro-LED epitaxial wafers based on low power plasma discharge

A majority of electroluminescence spectroscopy inspection systems for LED epitaxial wafers are currently focused on conductive probe contact methods. However, the huge number of bead chips and the difficulty in performing point contact due to the microsize largely limit its application in the field of Micro-LED epitaxial wafers. In order to improve the efficiency of electroluminescence spectroscopy inspection of Micro-LED epitaxial wafers, this study proposed a practical method for contactless electroluminescence of Micro-LEDs, which can achieve contactless electroluminescence while ensuring the characteristics of nondestructive inspection. The basic element of the method is the generation of an induced electric potential by a conducting probe under a high frequency alternating electromagnetic field. The high frequency skin effect of the conductor causes a corona discharge arc at the tip of the probe. The electrical and optical properties of the contactless electroluminescence were analyzed by experiments. The results show that the error in the measured value of the spectral distribution is less than 2%. The system has an ultra-high dynamic inspection range, demonstrating the capability of efficient scanning and inspection.