A Practical Example of GaN-LED Failure Cause Analysis by Application of Combined Electron Microscopy Techniques.

In this paper, we report a failure case of blue LEDs returned from a field application, and propose a practical way to identify the physical and structural reasons for the observed malfunction by a combination of different electron microscope techniques. Cathodoluminescence imaging and electron beam induced current (EBIC) imaging are employed in order to visualize conductive paths through the device in conjunction with subsequent energy dispersive x-ray analysis (EDS), revealing a metal deposition along cracks in the semiconductor layer which short-circuit the device. We demonstrate that the electron beam induced current imaging, in conjunction with other microscopic and analytical techniques at µm scale, is a powerful combination for clearly resolving and visualizing the cause of failure in the GaN LED chip. However, this represents a case study of a real application, which may not have been generally observed in laboratory testing environment.