Injection of Ballistic Hot Electrons and Cool Holes in a Two-Dimensional Electron Gas

We have constructed a novel magnetic spectrometer to study the dynamics of hot electrons and cool missing electron states injected by quantum point contacts in the two-dimensional electron gas of a GaAs-AlxGa1-xAs heterostructure. The mean free path of these quasi-particles is found to be longer than recent theoretical estimates. The injection energy of the particles is found to be anomalously low as the point contact approaches pinch-off, and also for high bias voltages.

Hot-electron spectrometry with quantum point contacts

Ballistic transport of electrons over several micrometers with excess energy of up to the order of the Fermi energy has been observed in the two-dimensional electron gas of a GaAs-AlxGa1–xAs heterostructure. Quantum point contacts in an electron-focusing geometry have been used as a novel magnetic spectrometer to measure directly the kinetic energy of injected electrons. The observed energy gain is linear in the total applied voltage, and the slope allows a determination of the local voltage drop over the point contact.