Long-Lived Acoustic Phonon and Carrier Dynamics in III-V Adiabatic Cavities

Evidence of strongly confined coherent acoustic phonons inside high quality factor phononic cavities that exhibit tailored phonon potentials is provided. Using GaAs/AlAs quasiperiodic superlattices, functional phonon potentials are realized by adiabatically changing the layer thicknesses along the growth direction. Room temperature ultrafast vibrational spectroscopy reveals discrete phonon modes with frequencies in the range of approximate to 96-101 GHz. Additionally, it is confirmed that phononic cavities impact the energy loss rate of the photoexcited carriers, as evidenced by time-resolved photoluminescence measurements. These results highlight the potential of concurrently engineering optoelectronic and phononic properties for a range of novel applications. Ultrafast vibrational spectroscopy shows that adiabatically changing layer thicknesses in GaAs/AlAs superlattices results in discrete phonon modes with coherence times on the order of nanoseconds, in the frequency range 96- 101 GHz. Time resolved photoluminescence suggest these phonon modes slow the energy loss of photoexcited carriers, highlighting the potential of concurrently engineering phononic and optoelectronic properties. image