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 Alₓ{Ga}_{1{{-}}x}$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}vₛ and the attenuation coefficient {κ} satisfy the well known equation ({Δ}vₛ/vₛ)-(i{κ}/q)=(α²/2)/[1+iσₓₓ(q,{ω})/{σ} ₘ], where σₓₓ(q,{ω}) is the complex conductivity at wave vector q and frequency {ω}=vsq with vₛ the velocity of the SAW. The coefficients {α} and σₘ are calculated and it is found that {α} has a nontrivial dependence on the product qd. {} 1996 The American Physical Society.