Editing Quantum well (section)

== Description and overview ==

One of the simplest quantum well systems can be constructed by inserting a thin layer of one type of semiconductor material between two layers of another with a different band-gap. Consider, as an example, two layers of [[Aluminium gallium arsenide|AlGaAs]] with a large bandgap surrounding a thin layer of [[Gallium arsenide|GaAs]] with a smaller band-gap. Let’s assume that the change in material occurs along the ''z''-direction and therefore the potential well is along the ''z''-direction (no confinement in the ''x–y'' plane.). Since the bandgap of the contained material is lower than the surrounding AlGaAs, a quantum well (Potential well) is created in the GaAs region. This change in band energy across the structure can be seen as the change in the potential that a carrier would feel, therefore low energy carriers can be trapped in these wells.<ref name=":1" /> [[File:MCM QW1 GaAs.png|thumb|The band structure diagram in a quantum well of GaAs in between AlGaAs. An electron in the conduction band or a hole in the valence band can be confined in the potential well created in the structure. The available states in the wells are sketched in the figure. These are "particle-in-a-box-like" states.]]

Within the quantum well, there are discrete [[Stationary state|energy eigenstates]] that carriers can have. For example, an electron in the [[Valence and conduction bands|conduction band]] can have lower energy within the well than it could have in the AlGaAs region of this structure. Consequently, an electron in the conduction band with low energy can be trapped within the quantum well. Similarly, holes in the valence band can also be trapped in the top of potential wells created in the valence band. The states that confined carriers can be in are [[Particle in a box|particle-in-a-box]]-like states.<ref name=":0" />