定义：一种薄层结构，在一维方向上限制载流子。
 
量子阱是一种薄层结构，可以在一维方向上，也就是垂直于薄层表面的方向上限制粒子（通常为电子或者空穴），而在其它方向上粒子的运动不受限制。 
量子阱对粒子的限制是一种量子效应。它对受限制粒子的态密度有很大的影响。
对于矩形的量子阱来说，其态密度在特定能量间隔内是常数。 
量子阱通常也是由薄层半导体介质制作的，嵌入在更宽带隙的半导体薄层之间（例如，GaAs量子阱嵌在AlGaAs中, 或者InGaAs嵌在GaAs中）
这种量子阱的厚度在5-20nm之间。这种薄层结构可以采用分子束外延（MBE）或者金属有机化学气相沉积（MOCVD）方法制备。
电子和空穴都可以被限制在半导体量子阱中。
在光学泵浦的半导体激光器（垂直外腔表面发射激光器）中，大部分的泵浦光在量子阱周围的薄层中被吸收，然后产生的载流子就被量子阱捕获。 
如果量子阱受到应力，可能是由晶格失配引起的（例如，InGaAs量子阱嵌入在GaAs中），电子态被改变，这在激光二极管中也非常有用。 
半导体量子阱通常用在激光二极管的有源区，其中它被夹在两个具有更高带隙能量的宽的薄层之间。
这些包层类似于波导，如果带隙能量差足够大，电子和空穴就被有效的被限制在量子阱中。量子阱也可以用作半导体饱和吸收反射镜和电吸收调制器中的吸收器。 
如果需要很大的光学增益或者吸收，可以使用多个量子阱，它们的间隙需要足够大以避免波函数之间的交叠。

Definition: thin layers confining carriers in one dimension

A quantum well is a nanometer-thin layer which can confine (quasi-)particles (typically electrons or holes) in the dimension perpendicular to the layer surface, whereas the movement in the other dimensions is not restricted.

The confinement is a quantum effect. It has profound effects on the density of states for the confined particles. For a quantum well with a rectangular profile, the density of states is constant within certain energy intervals.

A quantum well is often realized with a thin layer of a semiconductor medium, embedded between other semiconductor layers of wider band gap (examples: GaAs quantum well embedded in AlGaAs, or InGaAs in GaAs). The thickness of such a quantum well is typically ≈ 5–20 nm. Such thin layers can be fabricated with molecular beam epitaxy (MBE) or metal–organic chemical vapor deposition (MOCVD). Both electrons and holes can be confined in semiconductor quantum wells. In optically pumped semiconductor lasers (→ vertical external-cavity surface-emitting lasers), most pump radiation may be absorbed in the layers around the quantum wells, and the generated carriers are captured by the quantum wells thereafter.

If a quantum well is subject to strain, as can be caused by a slight lattice mismatch (e.g., for InGaAs quantum wells in GaAs), the electronic states are further modified, which can even be useful in laser diodes.

Semiconductor quantum wells are often used in the active regions of laser diodes, where they are sandwiched between two wider layers with a higher band gap energy. These cladding layers function as a waveguide, while electrons and holes are efficiently captured by the quantum well (separate confinement), if the difference in bandgap energies is sufficiently large. Quantum wells are also used as absorbers in semiconductor saturable absorber mirrors (SESAMs), and in electroabsorption modulators.

If a large amount of optical gain or absorption is required, multiple quantum wells (MQWs) can be used, with a spacing typically chosen large enough to avoid overlap of the corresponding wave functions.

Bibliography