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This work reports the design, manufacturing and numerical simulation approach of a 6-pixel (4.5 mm2/pixel) electroluminescent quantum dot light emitting device (QLED) based on CuInS2/ZnS quantum dots as an active layer. The QLED device was fabricated using a conventional multi-layer thin film deposition. In addition, the electrical I–V curves were measured for each pixel independently, observing how the fabrication process and layer thickness have an influence in the shape of the plot. This experimental device, enabled us to create a computational model for the QLED based on the Transfer Hamiltonian approach to calculate the current density J (mA cm−2), the band diagram of the system, and the accumulated charge distribution. Besides, it is worth highlighting that the simulator allows the possibility to study the influence of different parameters of the QLED structure like the junction capacitance between the distinct multilayer set. Specifically, we found that the Anode-HIL interface capacitance has a greater influence in the I–V curve. This junction capacitance plays an important role in the current density increase and the QLED turn-on value when a forward voltage is applied to the device. The simulation enabled that influence could be controlled by the selection of the optimal thickness and transport layers during the experimental fabrication process. This work is remarkable since it achieves to fit simulation and experiment results in an accurate way for electroluminescent QLED devices; particularly the simulation of the device current, which is critical when designing the automotive electronics to control these new nanotechnology lighting devices in the future. [ABSTRACT FROM AUTHOR]

In this work, we propose a correction to the effective mass approach (EMA) to be used in Si quantum dot simulations. This correction tries to connect the different ways of modeling quantum dots within tight binding (considering the actual positions of the atoms and using additional atoms to passivate the surfaces) with those within the EMA, adapting the size of the simulated quantum dots to take the difference into account. With this aim, we implemented a 6×6 k·p calculation for the valence band and used a nonparabolic and anisotropic model for the conduction band to study hole and electron confinement, respectively. We then tested and used a very fast computational algorithm to obtain the electron and hole spectra in both cubic- and spherical-shaped quantum dots. [ABSTRACT FROM AUTHOR]

In this work we formulate the nonparabolic Schrödinger equation for a quantum dot in order to explore the main features of the carriers in these systems. In addition, we present a fast iterative numerical algorithm to solve it, obtaining the energy levels and envelope functions. We also model the electrostatic potential profile in a manner that makes it possible to discuss the effects of stronger confinements on the results. To demonstrate a practical implementation of this algorithm, we carry out an investigation into the effects of nonparabolicity of the valence band on the eigenstates of a Si quantum dot. Finally, we fit our results, using power expressions to relate the energy levels to the size of the cubic quantum dots, thus demonstrating the relevance of nonparabolicity. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present an improvement on the normalized plane-wave method, for use in studies on carrier confinement in quantum dots. This alternative approach has two main advantages: it noticeably increases the accuracy of the calculations by removing the barrier surrounding the dot under study and it dramatically decreases the computation times. As we will demonstrate, this new approach is obtained from a simple analysis of the calculations. We use this algorithm to study hole confinement in spherical Si quantum dots, and from it we propose a correction to the Effective Mass approach to be used in Si quantum dot simulations. With this technique we obtained results comparable to those calculated by the Tight-Binding method but using less computational resources. [Copyright &y& Elsevier]

Abstract: In this work we present a fast and accurate genetic algorithm to determine the envelope functions and eigenenergies of the ground states of electrons and holes in low-dimensional complex semiconductor structures. We have developed the theoretical formalism of the algorithm in a general way in order to make it easy to include arbitrary nonparabolic and anisotropic band profiles in the calculations. From these results, calculation of the bandgaps of nanostructures can be carried out efficiently. Besides presenting and testing the algorithm, we calculate the ground state of electron and holes in two-dimensional quantum dot arrays, taking nonparabolicity and anisotropy into account. [Copyright &y& Elsevier]

The photon absorption coefficient in the arrays of InAs quantum dots embedded in GaAs is investigated. The influence of size and shape of the quantum dots on the miniband structure is analyzed. A detailed study is carried out in order to understand the physics relating to the absorption. The influence on the absorption coefficient due to the difference of energies between the lowest minibands, the joint density of states and the features of the wavefunctions are investigated in order to shed light on the phenomenon and understand it. The existence of thresholds in the absorption coefficient in the far infrared region, related to the shape of the quantum dots, is finally revealed, thus demonstrating that it may be an element to use both in future applications and in characterization of the materials. [ABSTRACT FROM AUTHOR]