As described for non-destructive characterization, the destructive chemical and physical characterization mechanism will also permit the understanding of the relationship between the microscopic material degradation, the physical parameters and the device failure. In this case, many samples, of the same characteristics, have to be degraded at the same time since the samples will be destroyed for final characterization.
1. Destructive characterization techniques will follow on the samples submitted to nondestructive techniques. These measurements can be carried out at different laboratories in parallel. Destructive techniques will enable to detect degradation at buried interface and in the bulk by relying on tools that than sputter in parallel to the analysis. The tools that are currently available allow to analyse structural and interdiffusion processes on cross-sections applying microscopy techniques, like transmission and scanning electron microscopy (TEM and SEM, respectively). Change in chemical composition or oxidation state of the compound as well as interdiffusion processes are X-ray photoelectron spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). Impact of interdiffusion and changes at the interfaces on the mechanical strength of the devices will be measured double cantilever beam (DCB) tests. These tools are only available at few locations and they are often time-consuming and costly. Therefore the experts in WG3 and WG4 will ensure selection of the most relevant samples.
2. Modelling of the opto-electrical response of the degraded devices will be implemented combining exiting device modelling expertise and insight about the degradation mechanisms.
The characterization techniques in WG4 will generate parameters such charge carrier mobility, excited state lifetime and diffusion length, energy levels, etc. that are direct input for the simulation. The modelling will aim to validate and complement the understanding extracted in WG5.
3. Experimental results generated in WG5 will also enable the modelling of the chemical interactions, material diffusion and other processes in the device during degradation. This can assist the understanding of the failure at the microscopic level. It will furthermore contribute to prediction of device performance behaviour at different stress levels which can be the foundation for accelerated lifetime models.
To describe the different degradation mechanism observed by destructive characterization analyses. To compare the opto-electrical modelling of device degradation in order to experiment results and discussion of relevant differences. To suggest how to prevent these degradation routes and possible ways to derive accelerate testing methods for these particular processes. As also described for non-destructive analyses, the results obtained in this WG will be combined with those observed in WG4 in order to arrive to more comprehensible degradation mechanisms.