VOLTAGE TUNABLE ACOUSTOELECTRIC INTERACTION IN GAAS ALGAAS HETEROJUNCTIONS/

The interaction between surface acoustic waves and high mobility quasi -two-dimensional electron systems (2DES) in GaAs/AlGaAs heterojunction s with variable carrier density is investigated experimentally. In spe cially designed samples the strength of this acoustoelectric interacti on can be controlled via the field-effect induced variation of the car rier density of the 2DES. Since the sensitivity of surface acoustic wa ve experiments is particularly high at very low conductivities, the pr oposed technique will be an especially valuable tool for the investiga tion of 2DES with extremely low sheet carrier densities. We demonstrat e that the proper use of a metallic gate electrode does not conflict w ith the piezoelectric interaction between the mobile carriers confined in the heterostructure and the surface acoustic wave propagating on t he piezoelectric substrate. (C) 1994 American Institute of Physics.