The superposition principle is one of the cornerstones of physics. In low-dimensional systems, it is routinely used to model the potential profile. That is the case of coupled [Formula: see text]-doped quantum wells, for which, several works have studied the transport and optoelectronic properties. However, the Poisson equation determines the potential profile is not linear, and the superposition principle is not at all valid. The aim of this work is to correct some of the inconsistencies of the mentioned models for coupled [Formula: see text]-doped quantum wells. In the framework of Thomas–Fermi approximation, we calculated the potential profile, the wave functions, the energy values and the relative absorption coefficient for the double system compared to an isolated delta system in terms of impurity density and distance between [Formula: see text]-wells. We found a red shifting in the absorption coefficient when the interlayer distances increase, in addition, an enhancement in the absorption coefficient is detected for a specific separation distance. Our results agree with ab-initio calculations reported for the electronic structure.

The effects of the interlayer distance on the nonlinear optical properties of n-type quadruple δ-doped GaAs quantum well were theoretically investigated. Particularly, the absorption coefficient and the relative refraction index change were determined. In the effective mass approach and within the framework of the Thomas–Fermi theory, the Schrödinger equation was resolved. Thereby, the subband energy levels and their respective wave functions were calculated. The variations in the nonlinear optical properties were determined by using the density matrix solutions. The achieved results demonstrate that the interlayer distance causes optical red-shift on nonlinear optical properties. Therefore, it can be deduced that the suitably chosen interlayer distance can be used to tune optical properties within the infrared spectrum region in optoelectronic devices such as far-infrared photo-detectors, high-speed electronic-optical modulators, and infrared lasers.

Within the framework of the Thomas-Fermi theory, the electronic structure and the nonlinear optical properties in n-type GaAs double delta-doped quantum wells where determined. In particular, was studied the effects of the distance between the doping layers and the hydrostatic pressure on the absorption coefficient and the change in the refractive index. It was found that the interlayer distance has an important effect on potential geometry, while the pressure lowers the bottom of potential. It was found that the influence of the interlayer distance (hydrostatic pressure) generates a red-shift (blue-shift) on the absorption peak and the refractive index change node. The results indicate that the optoelectronic properties in small interlayer distances (25–50 Å) show a high sensitivity to the changes of hydrostatic pressure, whereas for distances larger than 100 Å the effects of hydrostatic pressure are unimportant for the 1-0 transition. On the far-infrared regime, the effects of these parameters can be applied to tuning the position and amplitude of the resonant optical signals.

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In the framework of the Thomas–Fermi (TF) approach, a model for the p-type double-δ-doped (DDD) system in GaAs is presented. This model, unlike other works in the literature, takes into account that the Poisson equation associated with the system is nonlinear. The electronic structure is calculated for heavy and light holes. The changes in the electronic structure result of the distance d between the doped layers are studied. In particular, the relative absorption coefficient as well as the relative refractive index change is calculated as a function of the incident photon energy for heavy holes. The effect of the interlayer distance exhibits, in the absorption coefficient, a red shift of the peak position and a decrease in amplitude when the distance increases. In addition, the relative refractive index change node has a red shift as well as the interlayer distance increases. The calculations show that the effect of the separation between layers has a greater influence on the linear terms. These results are very important for theoretical calculations and engineering of optical and electronic devices based in δ-doped GaAs.