Resonant Tunneling through Single Electronic States and Its Suppression in a Magnetic Field

We observe resonant tunneling through single electronic states in a novel semiconductor device. At low temperatures, Lorentzian peaks of order but less than $\frac{e^2}{h}$ in magnitude are observed in the conductance versus Fermi energy of the device. As the temperature is increased, the peaks change in amplitude and width consistent with thermal broadening of the energy distribution of the electrons. An external magnetic field monotonically decreases the amplitude and reduces the widths of the peaks in accordance with a model based on isolated resonant wells.