Amplification of Ultrasonic Waves in Bulk GaN and GaAlN/GaN Heterostructures

Abstract

We report the results of calculations of ultrasonic amplification in bulk and 2D GaN, as a function of both ultrasound frequency and electron drift velocity. It is shown that GaN is in principle, a suitable material for the observation of acoustoelectric gain at applied fields corresponding to electron drift velocities, which are slightly higher than the sound velocity. As a result, acoustoelectric instabilities should prevail before the onset of other nonlinear effects associated with hot electron transport. However, because of the poor quality of current GaN material grown on sapphire, lattice attenuation is expected to be high and counteract the amplification in poor quality GaN, whereas a net amplification should be achieved in non-degenerate 2D GaN.

Phonon-Electron Interactions in Piezoelectric Semiconductor Bulk Acoustic Wave Resonators

“…Bulk GaN has an electron saturation velocity greater than 10 5 m/s, comfortably higher than the acoustic velocity by more than an order of magnitude 26 27 . Impact ionization effects are not expected till electric fields of at least 150 MV/m 28 , enabling large values of η before velocity saturation or breakdown.…”

“…This dynamic and reversible improvement in the Q of PS-BAW resonators can be distinctly observed on applying a DC electric field. Experimental work presented here has focused on GaN as it is a high-quality acoustic PS material predicted to be optimal for demonstrating acoustoelectric amplification 28 33 . Measured results presented here verify these predictions.…”

Q Amplification in Gallium Nitride Thickness-Mode Filters Using Acoustoelectric Effect

“…Efforts have been made to evaluate the viability of achieving acoustoelectric amplification in bulk GaN. Significant among these recent analyses is the work by Abdelraheem et al [9] and Mensah et al [10] who analytically demonstrated that GaN is a suitable material for the observation of acoustoelectric gain.…”