Features of recombination radiation temperature reduction in semiconductor quantum dots with extrinsic complexes

Abstract

Background. Semiconductor quantum dots, due to their unique optical properties, are a promising material for creating optoelectronic devices. At the same time, the devices’ parameters change significantly over a wide temperature range, which requires knowledge of the temperature dependence of both the band structure and the energy of impurity levels in quantum dots. In this case, the electron-phonon interaction acts as the most important mechanism for the temperature shift of energy levels. The purpose of this work is to theoretically study the effect of electron-phonon interaction on the temperature dependence of radiative recombination in an extrinsic complex ( A+ + e ) in a semiconductor quasi-zerodimensional structure. Materials and methods. The theoretical consideration of the temperature effect on the energy levels in a semiconductor quantum dot was carried out by a statistical method under the assumption that the main contribution to the temperature dependence comes from the electron-phonon interaction. The dispersion equation, which determines the binding energy of a hole in an extrinsic complex ( A+ + e ) in a spherically symmetric quantum dot, was obtained in the framework of the adiabatic approximation in the model of a zero-radius potential. The calculation of the spectral intensity of recombination radiation in a quasi-zero-dimensional structure with extrinsic complex ( A+ + e ) was performed in the dipole approximation taking into account the dispersion of the radius of quantum dots. The temperature dependence curves are plotted for the case of InSb-based quantum dots. Results. The temperature dependence of the binding energy in the complex ( A+ + e ) is calculated for various values of the quantum dot radius. It is shown that, with increasing temperature, the hole binding energy decreases, which is associated with the temperature “spreading” of the wave function of the quasistationary A+ -state under conditions of electron-phonon and hole-phonon interactions. It was found that with a decrease in the radius of a quantum dot, the binding energy of the A+ -state increases due to an increase in the energy of the ground state of the adiabatic potential of an electron. The dependence of the spectral intensity of the recombination radiation on the transition energy is calculated for various values of temperature. It was found that with increasing temperature, the threshold transition energy shifts to the short-wavelength region of the spectrum, and temperature quenching of the recombination radiation takes placeThis is due to a decrease in the overlap integral of the wave functions of the initial and final states of an electron due to an increase in the transition energy. Conclusions. The effect of electron-phonon interaction on recombination processes in extrinsic complexes ( A+ + e ) in a spherically symmetric quantum dot manifests itself in temperature reduction of the spectral intensity of the recombination radiation. The effect of reaching a “plateau” appears to be common to different photoluminescence mechanisms.

Keywords

• quantum dot
• extrinsic complex
• zero-radius potential method
• adiabatic approximation
• electron-phonon interaction
• intensity of recombination radiation