Observation of Plasmon-Optic Phonon Coupled Modes in GaAs/AlGaAs Resonant Tunneling Structures via Acoustic Phonon Decay Products

Using a nanosecond pulse technique to detect acoustic phonon decay products, we have observed plasmon-optic phonon coupled modes excited by tunneling electrons in the heavily doped collector of a double barrier resonant tunneling structure. From steps observed in the bias voltage dependence of the detected phonon flux we inferred the coupled mode energies to be $50$ and $30\mathrm{meV}$. Both modes decayed predominantly via lattice rather than electronic processes. Their widths were unexpectedly narrow, the result we believe of spatial inhomogeneity of collector carrier concentration.