Heterodyne mixing of millimetre electromagnetic waves and sub-THz sound in a semiconductor device

Abstract

We demonstrate heterodyne mixing of a 94 GHz millimetre wave photonic signal, supplied by a Gunn diode oscillator, with coherent acoustic waves of frequency ~100 GHz, generated by pulsed laser excitation of a semiconductor surface. The mixing takes place in a millimetre wave Schottky diode, and the intermediate frequency electrical signal is in the 1–12 GHz range. The mixing process preserves all the spectral content in the acoustic signal that falls within the intermediate frequency bandwidth. Therefore this technique may find application in high-frequency acoustic spectroscopy measurements, exploiting the nanometre wavelength of sub-THz sound. The result also points the way to exploiting acoustoelectric effects in photonic devices working at sub-THz and THz frequencies, which could provide functionalities at these frequencies, e.g. acoustic wave filtering, that are currently in widespread use at lower (GHz) frequencies.

Piezoelectric Response to Coherent Longitudinal and Transverse Acoustic Phonons in a Semiconductor Schottky Diode

“…The technical limitations of the experiment do not mean that Schottky diodes cannot detect signals at much higher frequencies when using specially designed microwave holders and smaller devices. Devices with Schottky contacts a few microns in size have capacitances of order 10 fF and have been shown to detect at frequencies up to at least 100 GHz [26]. The acoustic signal size in these devices is comparable to that seen in this work, showing that a decrease in device size to a few microns does not significantly impact the amplitude of the detected signal.…”

Coherent acoustic phonons in van der Waals nanolayers and heterostructures

“…For example, the control of phonon transport across a vdW interface could provide a strategy to probe and tune thermal conductivity for specific applications in electronics and thermoelectrics [47][48][49][50][51]. The interaction of coherent phonons with charge carriers could enable new routes for the generation of microwave frequencies as it is done in nanoelectromechanical (NEMS) systems in the MHz-GHz frequency range [52], in piezoelectric heterostructures for the sub-THz range [53], and traditional semiconductor devices such as Schottky diodes [11,54] and tunneling devices [12]. Also, due to strong elastic anisotropy and phonon quantization, 2D vdW layers could provide an ideal system for phonon nanoscopy and nondestructive sensitive imaging of molecules and cells coupled to the nanolayers by vdW forces.…”

A high electron mobility phonotransistor

“…3 . Applications of these coherent phonons include: fundamental studies of phonon transport and interactions in materials; [3][4][5][6][7] hypersonic probing of nanostructures [8][9][10] and single biological cells 11,12 with nanometre resolution; control of the optical, electronic and magnetic properties of materials and devices; [13][14][15] and generation and detection of sub-THz electromagnetic radiation 16,17 .…”