Avalanche Breakdown (Semiconductor)

IBM researchers invent a device that uses light to help computer chips to communicate. What I found interesting in this is the phenomenon of Avalanche Breakdown in Germanium.

From Wikipedia : "Most of the time, the electron and hole will just move to opposite ends of the crystal and stop. Under the right circumstances, however, (ie. when the voltage is high enough) the free electron may move fast enough to knock other electrons free, creating more free-electron-hole pairs (ie. more charge carriers), increasing the current. Fast-"moving" holes may also result in more electron-hole pairs being formed."

That is, in Germanium, an incoming light pulse frees a few charge carriers that, in turn, free others until the original signal is amplified many times.

More details:
http://www.nature.com/nature/journal/v464/n7285/full/nature08813.html
http://domino.research.ibm.com/comm/research_projects.nsf/pages/photonics.index.html
http://en.wikipedia.org/wiki/Avalanche_breakdown