Acoustic Nanostructures for Charge Carrier Confinement in GaAs/AlGaAs Multiple Quantum Wells

Quantum confinement of charge carriers in semiconductors is at the heart of next generation technologies for energy conversion, encryption and computation. We use picosecond-duration surface acoustic phonon pulses to produce lateral 2D and 3D carrier confinement in polar III-V semiconductor quantum wells. Shear strain and dilatation generated by the phonon pulses vary with depth below the sample surface, locally deforming the valence and conduction bands to produce lateral confinement in the plane of a quantum well that is externally controllable. We grew a GaAs/AlGaAs heterostructure containing three quantum wells, 5, 7, and 10 nm wide, at depths of 14, 49, and 112 nm beneath the sample surface respectively, to coincide with different piezoelectric field strengths. We verify carrier confinement and transport using metallic gratings on the surface of the sample to generate and detect surface acoustic phonons. These gratings modulate light absorption on length scales below the optical diffraction limit. Our approach enables a spectrally selective scheme for generating surface acoustic phonons 20 – 200 nm in wavelength. Length scales at the lower end of this range are associated with quantum confinement.