Abstract
An asymmetric quantum well consisting of one narrow and one wide well separated by a thick barrier is investigated. We calculate the change in the position expectation values of an electron in the first three quasibound states of the structure as a biased voltage increases. The value in the first quasibound state, which is the ground state of the wide well, shifts toward the right wall of the well. It has been found earlier that for a certain applied voltage, the first and second states of this whole structure, which are actually the ground state of the narrow well and the first-excited state of the wide well, respectively, coincide to give rise to resonant tunneling. At this resonance voltage, we see that the most probable position to find an electron in the second and third quasibound states lies in the barrier separating the two wells. Furthermore, these two states interchange their identities, meaning that the ground state of the narrow well becomes the first-excited state of the wide well and vice versa. We also calculate the oscillator strengths for transitions from the ground state of the wide well to the ground state of the narrow well and the first-excited state of wide well, and from the ground state of the narrow well to the first-excited state of the wide well. A similar conclusion can be drawn regarding the interchange of identities between the second and third quasibound states of the structure from the changes in oscillator strengths as a function of applied voltage. The oscillator strength for the transition from the ground state of the narrow well to the first-excited state of the wide well peaks at the resonant voltage.
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