Optical-Phonon Emission in Ballistic Transport through Microchannels of InGaAs

We have observed an oscillatory conductance in electrical transport through In-InGaAs contacts, corresponding to a series of dips in the I-V characteristic for both bias polarities at eV~nω₀, where n are integers and ω₀ is the LO-phonon energy of InGaAs. We explain the data by successive LO-phonon emission in high-field transport of ballistic electrons through microchannels of In-GaAs and point out that the experiment is a solid-state analog of the Franck-Hertz experiment.