Review of microwave electro-phononics in semiconductor nanostructures

Electro-phononics aims at developing devices which transform high frequency acoustic waves into electrical or microwave signals and back. This would eliminate the need for expensive and nonportable mode-locked lasers in phononic experiments increasing their ease and portability. The present review describes the main achievements in electro-phononics during the last decade. The first three sections of the review concern well developed ultrasonic and picosecond acoustic methods. While the next three sections give a review of recent experiments with various semiconductor nanodevices which allow the detection and generation of coherent acoustic phonons. Depending on the design of the electro-phononic device, it becomes possible to measure the actual or rectified temporal evolutions of the high-frequency acoustic field. A variation on these techniques is to exploit heterodyne mixing of coherent phonons with microwaves, it is then possible to perform sub-THz phonon spectroscopy experiments by lowering the frequency of the detected signal and using GHz detection electrical techniques. A further interesting approach is the phononic chip where various electro-phononic devices are integrated into a single complex nanostructure. Electro-phononic principles of the generation of THz phonons are developed utilizing the unique properties of doped semiconductor superlattices.