| Summary: | Background. Impurities of various chemical elements inevitably arise in the process
of manufacturing semiconductor nanostructures, or are introduced purposefully to
change their transport and optical properties. Moreover, most of impurities can have not
one, but two or more electrons in a bound state. In this case, electronic correlations begin to
play an important role, due to which one of the fundamental reactions is possible - the process
of double photoionization of an impurity atom. The purpose of this research is to calculate
the first ionization potential of a two-electron impurity center in a semiconductor
quantum well using the variational method, as well as a theoretical study of the effect of
electronic correlations on double photoionization spectra of two-electron impurity centers
in multi-well quantum structures. Materials and methods. The binding energy and the first
ionization potential of a two-electron atom were calculated by the variational method,
where the second ionization potential was taken as an empirical parameter. The expression
for the coefficient of impurity absorption of light was obtained in the dipole approximation
taking into account the dispersion of the width of the quantum wells. Results. The method
of the zero-radius potential is generalized to the case of two-electron impurities with an effective
nuclear charge equal to zero in semiconductor quantum wells. Within the framework
of a semiempirical model, an analytical expression for the first ionization potential of
a two-electron impurity center is obtained by the variational method. In the dipole approximation,
the coefficient of impurity absorption of light is calculated for the photoionization
of a two-electron impurity in a multi-well quantum structure with one photon. Conclusions.
It is shown that, due to spatial confinement in a quantum well in one direction, there is an
increase in electron correlations, which leads to higher threshold values of the second ionization
potential than in quantum dots and, as a consequence, to more stringent conditions
for the existence of two-electron impurity states. It was also shown that a decrease in the influence
of the quantum size effect and an increase in the electron correlation in multi-well
quantum structures as compared to quasi-zero-dimensional structures lead to a transformation
of the absorption curve, which is expressed in an increase in the gap between the
peaks of the two-humped profile of the spectral curve.
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