We report the first observation of the resonant tunneling features associated with the quantized levels in the accumulation layer of the double‐barrier resonant tunneling structure (DBRTS) with undoped electrodes. This quantum effect causes additional kinks in the current‐voltage (I‐V) characteristic and an increasingly enhanced oscillation behavior in the differential conductance‐voltage (G‐V) curve. Three discrete quantum levels have been observed based on the room‐temperature G‐V curve. Our measurements are made without the presence of magnetic field and thus the experimental results are totally different from the magneto‐oscillation.
