Widely tuneable quantum wire arrays in MISFET-type heterojunctions with a stacked gate

Abstract

A stacked gate technique is applied to study electronic excitations in electron quantum wire, quantum dot and antidot arrays in GaAs/AlAs MISFET-type heterojunctions at far-infrared frequencies. The gate configuration consists of a finely (period a ⩾ 250 nm) patterned bottom electrode on the surface of the heterostructure, a dielectric spacer and a homogeneous top gate. An electron grating is induced at the heterostructure interface either beneath the strips or beneath the gaps of the grating gate. With the fields induced by the top gate the confining potential can be controlled nearly independently of the electron density in quantum wires below the bottom gate. This is demonstrated by far-infrared studies of the dimensional resonances in the wires. In a perpendicular magnetic field we observe a very pronounced splitting of the dimensional resonance. We study this behaviour as a function of wire separation and potential form and find this splitting to reflect the anharmonicity of the confining potential.