Resonant tunneling and confining phenomena in symmetrical rectangular quadruple-barrier structures

Resonant tunneling is studied theoretically in symmetrical rectangular quadruple-barrier structures. Analytical expressions for the transmission coefficient and the resonance condition are derived. Two independent resonance conditions are obtained especially for structures with four identical rectangular barriers, which may be favorable for resonant tunneling device fabrication. It is found that tunneling with transmission peak smaller than unity (under-unity resonance) may occur when the outer barrier becomes thinner than the inner one; resonant tunneling with unity transmission (unity resonance) occurs when the outer barrier width is thicker than or equal to the inner barrier width. Wave functions of an electron at the resonance energy level are calculated and the confining phenomenon is studied.