High speed diode detector

Can Schottky diode's be used for detection at very high frequencies? Not low signal work but for doing basic detection close to a transmitting source? According to Wikipedia the switching time for a fast Schottky can be 100ps. That's in the area of 10Ghz. What about half that, quarter that?

Yes. Google for "microwave diode" for more examples:
http://www.advancedsemiconductor.com/diodes/schottky_barrier_mixer_detector.shtml

I've used them up to 2.5GHz with good results. I believe they can go much higher than that frequency.