ABSTRACT
The split-gate electron waveguide with delta-doping layers as shown in Figure 3 (a) was fabricated and analysed. The epilayers were grown by MBE [3] and the Si doped delta doping layers are indicated by the thick lines within AlGaAs (x=0.3) layer. The split-gate spacing is 3000 A. Figure 3(b) shows the variations of the eigen energy levels as the gate voltage varies from -3.2V to -2.2V with an ambient temperature of 310 mK. The low temperature ambient was obtained by He cryogenic system [5]. The arrows indicate where the energy levels cross over the Fermi energy level. In one dimensional transport system, one can expect one additional quantum conductance G0=2e2/h whenever one additional quantum state is available [6]. This happens when the eigen energy levels cross the Fermi level. The bottom of Figure 3 (b) shows the measured conductance in the split-gate electron waveguide along with the calculated quantum conductance. In the calculation, the surface charges are modelled after the unified defects model [7] and the carrier concentrations in 1 dimensional region is obtained from numerical integration of the Fermi-Dirac integrals. This approach is more accurate than using the Boltzman or Joyce-Dixon approximation. The conductance characteristics obtained from the experimental data and the analysis agree well up to the first 3 steps. Measured steps for the higher subbands are smeared out due to the scattering.
