Theoretical analysis of tunneling phenomenon in asymmetrical triple-barrier structures with outer wells

The impact of the outer wells on tunneling characteristics is theoretically studied in a new structure with outer wells consisting of wells on both sides of an asymmetrical triple barrier structure. First, the theoretical equation for the transmission coefficient is derived and the resonance conditions are studied. It is found that resonance is not related to the existence of the outer wells and is governed by the two resonance conditions independently existing in the two wells between the barriers. Second, the dwell time of electrons at the two resonant energy values is analyzed. The dwell time in the triple barrier structure with outer wells is compressed to about 14% at the maximum in comparison with the dwell time in the triple barrier structure without outer wells. Even if the dwell time is compared with that in the structure with a prewell, which is a conventional way of reducing the dwell time, a reduction to about 60% is realized. Also, with regard to the current density versus voltage characteristics for the structure with outer wells, it is found that a large current flows at a lower voltage than in the structure without outer wells. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(1): 20–31, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20275