Using the new experimental technique of hot-electron spectroscopy we have, for the first time, observed electrons in extreme nonequilibrium. When the transit-region width is comparable to the calculated hot-electron mean free path, two peaks are observed in the measured spectrum. The high-energy peak corresponds to quasiballistic electrons suffering few, if any, collisions in the transit region. The low-energy peak is due to excitation of the Fermi sea by the injected hot electrons.

• Received 8 July 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.2071