Resonant tunneling through a symmetric triple-barrier structure

We consider tunneling of electrons through a triple-barrier structure. We focus our attention on the transmission coefficient T when the incident energy of the electrons is resonant with one of the quasibound energy levels of the structure. Although it is widely recognized that for a symmetric double-barrier structure T goes to unity at resonance, we shall show that this is not always the case for a symmetric triple-barrier structure in which the external barriers are half the width of the internal barrier.