Tunneling spectroscopy of an electron waveguide

On an AlGaAs/GaAs heterostructure, we have implemented a unique ``leaky'' electron waveguide with a thin tunneling barrier as one of its confining boundaries. The current flowing through the waveguide as well as the 1D to 2D tunneling current leaking out the thin side barrier were independently measured as the electron density in the waveguide was modulated. The tunneling current shows very strong oscillations lined up with the 2e^2/h conductance steps for the waveguide current. A proposed explanation is that the oscillations are a result of the 1D density of states sweeping through the Fermi level.