Analysis of the effect of polarization traps and shallow impurities on the interlevel light absorption of quantum dots

TL;DR

This paper investigates how polarization traps and shallow impurities influence the light absorption properties of spherical CdS/SiO₂ quantum dots, highlighting the role of surface states and size dispersion.

Contribution

It introduces a model accounting for polarization traps and surface states in quantum dots, providing new insights into their impact on light absorption spectra.

Findings

Surface states appear at small QD radii.

Surface states contribute to absorption in different spectral ranges.

Size dispersion affects the absorption coefficient.

Abstract

A spherical quantum dot (QD) heterosystem CdS/SiO$_2$ has been studied. Each QD has a hydrogen-like impurity in its center. Besides that, it has been accounted that a polarization trap for electron exists at the interfaces due to the difference between the QD and matrix dielectric permittivity. It has been defined that for small QD radii there are surface electron states. For different radii, partial contributions of the surface states into the electron energy caused by the electron-ion and electron-polarization charges interaction have been defined. The linear light absorption coefficient of noninteracting QDs has been calculated taking into account the QD dispersion by the size. It is shown that the surface states can be observed into different ranges of an electromagnetic spectrum.