The design of several semiconductor devices of high technological content, such as quantum well infrared photodetectors (1), quantum dot infrared photodetector (2), and quantum cascade laser, QCL (3), depends on their bandstructure. The detailed design of the structures responsible for the proper operation of the device is sometimes named band engineering (4). These semiconductor structures are composed by several layers of different semiconductor materials, each one of the order of nanometers of thickness. These layers give origin to a series of heterojunctions in the interfaces due to the mismatch of the crystalline structure of each layer, defining a series of quantum wells and barriers. Usually, the conductivity of these semiconductor structures is increased by doping all or only selected layers. The properties of a giving structure depend on some parameters, such as, the material and thickness of each layer, the number and sequence of layers, and the kind and concentration of doping material used in each layer. In this scale, quantum effects are the responsible for the properties of such structures.
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