Demediuk R. Rearrangement of space quantization energy levels in delta-doped quantum wells

The influence of ionization of the delta layer of a shallow impurity located within a quantum well on the rearrangement of energy levels in this quantum well is theoretically investigated. An example of a combination of two types of quantum wells, rectangular (formed by the heterounctions) and V-shaped (formed by impurity delta-layer), shows that it is possible to change the energy distance between space-quantization levels in an existing quantum well by ionizing the delta layer of a shallow impurity. As the ionization degree rises, free electrons appear at space-quantization levels in the quantum well, and positive ions are created within the delta layer that form the Hartree potential superimposed on the rectangular potential profile. Thus, obtained a new energy profile of the existing heterostructure, with a new set of space-quantization levels. This effect is interesting and potentially useful, because this change has the influence on the optical transitions between few first levels. Using the self-consistent method, the influence on the rearrangement of levels in the quantum well of the following parameters was investigated: quantum well width, delta doping position, delta layer thickness, the initial concentration of impurities, the distribution of impurities in the delta layer, and ionization degree. The influence of ionization of the delta layer of impurities on the intersubband absorption of a quantum well has been investigated. It was found that the appearance and subsequent change of the Hartree potential due to ionization of the delta layer leads to significant changes in the overall intersubband absorption coefficient. The idea of creating a modulator of THz radiation on the basis of delta-doped quantum wells is formulated and substantiated. The optical properties and the tuning range of the potential device at different parameters of the quantum wells it used, were investigated. As a result of the study we can conclude that even at the design stage of the device can predict its characteristics, such as: the width of the tuning range and the possibility of simultaneous modulation of several THz bands.