I got a paper to review and the authors of this paper already published a conference proceedings on the same topic but supposedly a different device. When comparing the figures of the conference proceedings and the submitted paper it becomes apparent that the data is exactly the same. This should not be possible as even the noise patterns are agreeing and the device structure is different enough to show different results. What are my options?
I didn't quite understand the nuances involving "different device", but if I have the rest right: you've observed that the data of the present submission is identical to that of a past submission. The present submission involves something different enough so that identical data is not plausible, and therefore you strongly suspect that the data included in the present submission is not legitimate. Is that it?
If so, I see just one reasonable option: bring this information to the attention of the editors. It is serious enough that you need not (and perhaps should not) make a recommendation of acceptance or rejection: this needs to be resolved first.