Generation and Propagation of Superhigh-Frequency Bulk Acoustic Waves in GaAs
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2019-10-07
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Coherent superhigh-frequency (SHF) vibrations provide an excellent tool for the modulation and control of excitations in semiconductors. Here, we investigate the piezoelectric generation and propagation of longitudinal bulk acoustic waves (LBAWs) with frequencies up to 20 GHz in GaAs crystals using bulk acoustic-wave resonators (BAWRs) based on piezoelectric thin ZnO films. We show that the electroacoustic conversion efficiency of the BAWRs depends sensitively on the sputtering conditions of the ZnO films. The BAWRs are then used for the study of the propagation properties of the LBAWs in GaAs in the frequency and temperature ranges from 1 to 20 GHz and 10 and 300 K, respectively, which have so far not been experimentally accessed. We find that the acoustic absorption of GaAs in the temperature range from 80 K to 300 K is dominated by scattering with thermal phonons. In contrast, at lower temperatures, the acoustic absorption saturates at a frequency-dependent value. Experiments carried out with different propagation lengths indicate that the saturation is associated with losses during reflections at the sample boundaries. We also demonstrate devices with a high quality factor fabricated on top of acoustic Bragg reflectors. The results presented here prove the feasibility of high-quality acoustic resonators embedding GaAs-based nanostructures, thus opening the way for the modulation and control of their properties by electrically excited SHF LBAWs.
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Physical Review Applied, v. 12, n. 4, 2019.
