Calculations of the Acoustoelectric Current in a Quantum Well by Using a Quantum Kinetic Equation

An analytic expression for the acoustoelectric current (AC) j(ac) induced by electron-external acoustic wave interactions and electron-internal acoustic wave (internal phonons) scattering in a quantum well (QW) is calculated by using the quantum kinetic equation for electrons. The physical problem is investigated in the region ql >> 1 (where q is the acoustic wave number and l is the electrons mean free path). The dependence of the AC j(ac) on the external acoustic wave frequency. omega((q) over right arrow), the width of the QW L and the temperature T for a specific QW of AlGaAs/GaAs/AlGaAs is achieved by using a numerical method. The computational results show that the dependence of the AC j(ac) on the temperature T, the external acoustic wave frequency. omega((q) over right arrow), the width of the QW L is non-monotonic and that the peaks can be attributed to transitions between mini-bands n -> n'. The dependence of the AC j(ac) on the temperature T and the Fermi energy epsilon(F) is obtained, and a maximum of the AC j(ac) for epsilon(F) = 0.038 eV and omega((q) over right arrow) = 3 x 10(11) s(-1) seen at T = 50 K, which agrees with the experimental results for AlGaAs/GaAs/AlGaAs QWs. All these results are compared with those for normal bulk semiconductors and superlattices to show the differences. Finally, the quantum theory of the acoustoelectric effect in a quantum well is newly developed.