Double quantum well segments in ballistic diode bases

We consider space charge limited ballistic electron transport in short current-conducting channels formed by single and double quantum well segments. Independent contacts to the bottom-well and the top-well forming the double quantum well segment is stipulated. Three different structures are simulated: a resonant overlap structure, a resonant cover structure, and a coupler structure. It is shown that anode currents in these structures oscillate with increasing voltage across the structure, resulting in repeatedly N-shaped current-voltage (I-V) characteristics. A modulation level of the current oscillations is close to 100%. The shape of these oscillations is substantially asymmetric both for the overlap and the cover structures. The asymmetry is due to a very strong nonlinear space charge modulation, and N-shaped parts of I-V characteristics can become Z-shaped when a strong tunnel connection in the double quantum well segment takes place. In the coupler structure the modulation of partial anode currents flowing out through each of two anodes, which are independently contacted to the bottom-well and the top-well, occurs only. The space charge increases monotonously with the voltage. Justification criteria of the classic approach used in our calculations are discussed in detail.