Quantum well

Under a quantum well (English quantum well ) is defined as a potential course, the freedom of movement of a particle in one spatial dimension limits (usually in the z- direction), so that only a planar region (x, y plane ) can be occupied. The width of the quantum well largely determines the quantum states which can assume the particle. This leads in particular to the formation of energy levels (sub- bands ), i.e., the particles can have only discrete (potential) energy values ​​.

Production

In the semiconductor technology, quantum wells are formed by a layer of lower band gap semiconductor (e.g., GaAs) between two layers of larger band gap semi-conductor is embedded (for example, AlGaAs ). For this reason, the so- formed structure is often referred to as quantum film. A widely used method for preparing such structures is the molecular beam epitaxy, allows to control the layer thickness in the area of the individual layers (English monolayer ). To achieve good film qualities, is to be observed, among other things, that the materials used are compatible lattice, i.e., a sufficiently similar crystal structure ( lattice constant, inter alia ) have.

Applications

Due to the two-dimensional nature of the quantum well, the electrons and holes therein have a different density than in the three-dimensional crystal. By selectively doping ( highly mobile ) two-dimensional electron systems can be grown, find the applications such as HEMTs (german high - electron -mobility transistor). Other applications are eg quantum cascade lasers, diode lasers and quantum well infrared photodetector.