Conductance quantization in deep mesa-etched gate-controlled ballistic electron waveguides

Abstract

We present a theoretical study of the ballistic conductance in electron waveguides created by deep mesa etching from quantum-well structures with a two-dimensional electron gas (2DEG) in the well. The widths of the waveguides are controlled by gate bias voltages. We consider three different cases: the etched waveguide is completely covered by a gate [continuous gate (CG)], the gate is deposited on top of the waveguide [top gate (TG)], and when the gates are located on the etched side walls [side gate (SG)]. The number and periodicity of the quantized conductance steps, as well as the energy separation of the one-dimensional subbands near the Fermi level are determined as functions of the parameters of the device. The CG device provides a fairly periodic quantized conductance staircase. The highest subband separation is achieved for the TG device etched well below the 2DEG layer and for the SG device etched slightly below it.