Theoretical calculations have been used to assess the influence of both an external electric field and hydrostatic stress on the binding energy, impurity polarizability, as a function of the impurity position and density of states for shallow-donor impurities in a GaAs-(Ga, Al)As quantum well. The binding energy maximum is shifted toward the wall at z = -L/2 of the quantum well for increasing values of electric field (keeping a constant pressure) and increasing values of pressure (keeping a constant electric field). The polarizability follows closely the behavior of the binding energy so for smaller binding energies the polarizability is large showing a more delocalized electron cloud. Also, it has been observed that the density of states depends strongly on the applied hydrostatic stress and electric field. In the absence of an electric field the energy level is degenerate for symmetrical positions of the impurities with respect to the center of the quantum well. However, this degeneracy is broken when an electric field is applied in the growth direction of the structure. Associated with this, the density of states becomes richer in structure. IntroductionStudies of the effect of hydrostatic stress have proven to be invaluable in the context of the optical properties of semiconductors and their heterostructures [1-9]. For a given structure, the difference in energy between the type-I and -II transitions can be tuned with external hydrostatic pressure in a continuous and reversible manner. This makes possible an elucidation of the properties of various interband transitions.The application of an electric field in the growth direction of the heterostructure gives rise to a polarization of the carrier distribution and to an energy shift of the quantum states. Such effects may introduce considerable changes in the energy spectrum of the carriers, which could be used to control and modulate the output of optoelectronic devices [10,11]. Through the wave function, the polarizability measurements shed light on the dynamics of the carriers and optical properties in low dimensional heterostructures [12][13][14][15][16].In previous work [17] we have calculated the binding energy and impurity polarizability, as a function of both electric field and hydrostatic stress, for a shallow-donor impurity at the center of the single GaAs-(Ga, Al)As quantum well (QW). Here we extend the previous findings considering the binding energy, the polarizability, as a function of the impurity position and the density of impurity states (DOIS) for a uniform distribution of impurities. In this paper we use a variational scheme within the effective mass approximation.
ResumenLos estados electrónicos confinados en un punto cuántico de GaAs, de forma piramidal y cónica, se han investigado a través del enfoque cuasi analítico válido para ángulos pequeños y el método exacto de elementos finitos para incluir todos los ángulos y alturas. Se han reportado los resultados de la energía de confinamiento en función de la forma y el tamaño de ambas estructuras y finalmente se han comparado los valores aproximados con los exactos provenientes del método de elementos finitos. AbstractThe electronic states confined in a quantum dot, of GaAs, of pyramidal and conical shape have been investigated through the quasi-analytical approach, valid for small angles, and the finite element method to include all angles and heights. The results of the confinement energy have been reported according to the shape and size of both structures and finally the approximate values have been compared with the exact values obtained from the finite element method. Revista EIA, ISSN 1794-1237 / Año XV / Volumen 15 / Edición N.30 / Julio-Diciembre 2018 Publicación semestral de carácter técnico-científico / Universidad EIA, Envigado (Colombia)
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