Temperature Dependent Empirical Pseudopotential Theory For Self-Assembled Quantum Dots

TL;DR

This paper introduces a temperature-dependent empirical pseudopotential theory to analyze how temperature influences the electronic and optical properties of self-assembled quantum dots, accounting for lattice effects and matching experimental observations.

Contribution

It presents a novel temperature-dependent pseudopotential model that incorporates lattice expansion and vibrations to study quantum dot properties at finite temperatures.

Findings

Conduction band offset increases with temperature in heterostructures.

Valence band offset decreases and causes a type-I to type-II transition around 135 K.

Recombination energies exhibit red shifts consistent with experimental data.

Abstract

We develop a temperature dependent empirical pseudopotential theory to study the electronic and optical properties of self-assembled quantum dots (QDs) at finite temperature. The theory takes the effects of both lattice expansion and lattice vibration into account. We apply the theory to the InAs/GaAs QDs. For the unstrained InAs/GaAs heterostructure, the conduction band offset increases whereas the valence band offset decreases with increasing of the temperature, and there is a type-I to type-II transition at approximately 135 K. Yet, for InAs/GaAs QDs, the holes are still localized in the QDs even at room temperature, because the large lattice mismatch between InAs and GaAs greatly enhances the valence band offset. The single particle energy levels in the QDs show strong temperature dependence due to the change of confinement potentials. Because of the changes of the band offsets, the electron wave functions confined in QDs increase by about 1 - 5%, whereas the hole wave functions decrease by about 30 - 40% when the temperature increases from 0 to 300 K. The calculated recombination energies of exciton, biexciton and charged excitons show red shifts with increasing of the temperature, which are in excellent agreement with available experimental data.