Coupling of surface acoustic waves to a two-dimensional electron gas

When a surface acoustic wave (SAW) is coupled piezoelectrically to a two-dimensional electron gas (2DEG), a velocity shift and attenuation of the SAW are induced that reflect the conductivity of the 2DEG. This paper considers the case of an (Formula presented)(Formula presented)As heterostructure with a 2DEG a distance d from a (100) surface of the crystal where the SAW’s are propagated in the [011] direction at wave vector q. It is found that the velocity shift Δ(Formula presented) and the attenuation coefficient κ satisfy the well known equation (Δ(Formula presented)/(Formula presented))-(iκ/q)=((Formula presented)/2)/[1+i(Formula presented)(q,ω)/σ (Formula presented), where (Formula presented)(q,ω) is the complex conductivity at wave vector q and frequency ω=(Formula presented) with (Formula presented) the velocity of the SAW. The coefficients α and (Formula presented) are calculated and it is found that α has a nontrivial dependence on the product qd. © 1996 The American Physical Society.