Large Stark effects for transitions from local states to global states in quantum well structures

The electric-field dependence of the optical absorption for the type of quantum well structure in which one or more small wells are embedded in a big well is discussed. In such structures, local energy states confined by the small well(s) and global states confined by the big well have different electric-field dependences while their wave functions remain overlapped. Thus, a large Stark effect (large energy shift and oscillator strength) can be achieved for the optical transition from a local state to a global state. This concept of using the local and global states can be applied to both interband and intersubband transitions. For intersubband transitions, a typical 10-20 meV shift is predicted, compared to a reported 1.1 meV blue shift at the field 30 kV/cm. For interband transitions, the Stark shift is larger than that in the single quantum wells