Three-dimensional failure analysis of high power semiconductor laser diodes operated in vacuum

Abstract

The damaged region of a semiconductor laser diode that failed in a vacuum environment was analyzed using focused ion beam (FIB) serial sectioning, time-of-flight secondary ion mass spectrometry (ToF-SIMS), high resolution transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), energy dispersive x-ray spectroscopy (EDS), and nanodiffraction. The FIB nanotomography models and the TEM cross sections show a damage structure extending deep into the core and originating at the diode/antireflective (AR) coating interface. Nanocrystalline gold was detected at this interface using both TEM diffraction and EDS, and the localization of gold along the core at the diode/AR interface was corroborated using 3D ToF-SIMS. A thinning of the AR coating above the failure site was observed by TEM with a corresponding increase in carbon content on the AR surface detected with EELS. It is suggested that failure proceeded by pyrolysis of adsorbed hydrocarbons on the AR coating, which, in the presence of a high optical flux, contributed to carbothermal reduction of the AR coating. As the optical flux increased, thermal gradients facilitate metal migration, leading to larger gold clusters. These clusters are sites for deep level traps and may promote catalytic reactions.