Abstract
A detailed theoretical study of the optical absorption in doped self-assembled quantum dots is presented. A rigorous atomistic strain model as well as a sophisticated 20-band tight-binding model are used to ensure accurate prediction of the single particle states in these devices. We also show that for doped quantum dots, many-particle configuration interaction is also critical to accurately capture the optical transitions of the system. The sophisticated models presented in this work reproduce the experimental results for both undoped and doped quantum dot systems. The effects of alloy mole fraction of the strain controlling layer and quantum dot dimensions are discussed. Increasing the mole fraction of the strain controlling layer leads to a lower energy gap and a larger absorption wavelength. Surprisingly, the absorption wavelength is highly sensitive to the changes in the diameter, but almost insensitive to the changes in dot height. This behavior is explained by a detailed sensitivity analysis of different factors affecting the optical transition energy.
Highlights
Self-assembled quantum dots are employed as light absorbers in many optoelectronic devices, such as quantum-dot infrared photodetectors (QDIPs) [1,2], and intermediate-band solar cells (IBSCs) [3,4]
The inclusion of many-particle configuration interaction (CI) in calculating the energy transitions significantly improves the agreement between simulations and experiment for the doped quantum dot system
The simulations reproduce the experimental results with an error below 3%
Summary
Self-assembled quantum dots are employed as light absorbers in many optoelectronic devices, such as quantum-dot infrared photodetectors (QDIPs) [1,2], and intermediate-band solar cells (IBSCs) [3,4]. The optical properties of quantum dots (QDs) can be tuned through shape, dimensions and composition of the dots making them attractive for optoelectronic applications. Their sensitivity to normally incident light make them advantageous over other nanostructures, such as quantum wells, that are insensitive to normally incident light [2]. The absorption coefficient α(λ) of quantum dots is an important parameter that needs to be precisely designed for the proper operation of these devices. This study aims to fill the gaps in current absorption models, namely the atomistic strain and band structure calculations that are needed for accurate description of the bound states. The effects of alloy mole fraction of the strain controlling layer and quantum dot dimensions are discussed
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