Elementary excitations and quasi-two-dimensional behavior in a GaAs field-effect transistor

The elementary excitation modes in a narrow channel of conducting electrons in a special GaAs field-effect transistor are evaluated within the random-phase approximation. The system is found to be quasi-two-dimensional (2D) when the width of the channel is small, i.e., there are collective excitations with a dispersion very close to the strictly 2D form. In addition to the low-lying quasi-2D mode there are higher collective modes associated with the subband structure of the device.