Repetition of negative differential resistance in vertically integrated double-barrier resonant tunneling structures

We propose and demonstrate a novel operation in the vertical integration of double-barrier resonant tunneling structures (DBRTS's) in which the negative differential resistance (NDR) region can be repeated. When two DBRTS's are combined in series, one of which has a higher peak current, a lower valley current, and a larger operation range of voltage in the NDR region than those of the other, the current-voltage (I-V) characteristic shows three current peaks instead of the conventional two. This phenomenon is based on the fundamental requirement of current continuity in serially combined devices. This operation provides a method to obtain a large number of current peaks by using less DBRTS's.