Editing Quantum well (section)

=== Superlattices ===
[[File:GaAs-AlAs SL.svg|thumb|A heterostructure made of AlAs and GaAs arranged in a superlattice configuration. In this case, the resulting periodic potential arises due to the difference in band-gaps between materials.]]
A superlattice is a periodic heterostructure made of alternating materials with different band-gaps. The thickness of these periodic layers is generally of the order of a few nanometers. The band structure that results from such a configuration is a periodic series of quantum wells. It is important that these barriers are thin enough such that carriers can tunnel through the barrier regions of the multiple wells.<ref name=":3">Odoh, E. O., & Njapba, A. S. (2015). A review of semiconductor quantum well devices. ''Adv. Phys. Theor. Appl'', ''46'', 26-32.</ref> A defining property of superlattices is that the barriers between wells are thin enough for adjacent wells to couple. Periodic structures made of repeated quantum wells that have barriers that are too thick for adjacent wave functions to couple, are called multiple quantum well (MQW) structures.<ref name=":0" />

Since carriers can tunnel through the barrier regions between the wells, the wave functions of neighboring wells couple together through the thin barrier, therefore, the electronic states in superlattices form delocalized minibands.<ref name=":0" />  Solutions for the allowed energy states in superlattices is similar to that for finite quantum wells with a change in the boundary conditions that arise due to the periodicity of the structures. Since the potential is periodic, the system can be mathematically described in a similar way to a one-dimensional crystal lattice.