Papers by Matthias Auf der Maur
Solar Energy Materials and Solar Cells
Advanced Electronic Materials
Proceedings of the International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics
Advanced Functional Materials
Journal of Green Engineering
Multiscale approaches for electronic device simulation have become a subject of high interest dur... more Multiscale approaches for electronic device simulation have become a subject of high interest during the last decade. In this article we will give an overview on the current activities in the field. We will provide some practical examples from optoelectronics where multiscale simulations can be useful. Basic coupling schemes are discussed, and approaches for the combination of continuous models and models with atomistic resolution are described.
ACS Applied Materials & Interfaces
IEEE Transactions on Electron Devices
In this work we present a novel generalized multi-particle drift-diffusion model capable to overc... more In this work we present a novel generalized multi-particle drift-diffusion model capable to overcome some limitations imposed by the classic drift-diffusion model by taking into account multiple carrier populations. We demonstrate the model's ability and flexibility in simulating systems from different application contexts. We conclude that the developed multi-particle drift-diffusion model allows to investigate a wide range of complex mechanisms, such as sub-band charge transport calculation or intersystem crossing, that are crucial for the understanding and design of organic and inorganic semiconductor devices largely employed for both photovoltaics and light emitting applications.
Proceedings
Guidelines for the fabrication of nanoscale light-emitting diode arrays (i.e., nanoLED arrays) ba... more Guidelines for the fabrication of nanoscale light-emitting diode arrays (i.e., nanoLED arrays) based on patterned gallium nitride (GaN) with very small dimensions and pitches have been derived in this work. Several challenges during top-down LED array processing have been tackled involving hybrid etching and polymer-based planarization to yield completely insulated highaspect-ratio LED fin structures and support the creation of p-GaN crossing line contacts, respectively. Furthermore, simulations of the light emission patterns were also performed providing hints for enhancing the device designs. As a result, regardless of the required device processing optimization, the developed nanoLED arrays are expected to offer high potential as novel illumination sources in biomedical imaging and sensing applications (e.g., mini compact microscopes and wearable biological/chemical nanoparticle counters)
Journal of Applied Physics
ABSTRACT The aim of this work is to present a consistent model for simulation of organic solar ce... more ABSTRACT The aim of this work is to present a consistent model for simulation of organic solar cells (OPV) with a correct description of mobility, density of state, organic-metal contacts, and exciton. We simulate the photoconversion by means of an integration of the optical and electrical part: light absorption is calculated with a Transfer Matrix Model and the charge transport is computed using Drift Diffusion approach including the effect of energetically disorder materials. Most model parameters are directly taken from experiment. The model is used to study the effect of energetic disordered materials and cell thickness on the performance of the cell in terms of short circuit current, open circuit voltage, and fill factor. Based on the results of this model, it will be possible to design and predict the optimal thickness of OPV toward higher efficiencies.
Nanotechnology, Jan 7, 2017
We present a study of blue III-nitride light-emitting diodes (LEDs) with multiple quantum well (M... more We present a study of blue III-nitride light-emitting diodes (LEDs) with multiple quantum well (MQW) and quantum dot (QD) active regions (ARs), comparing experimental and theoretical results. The LED samples were grown by metalorganic vapor phase epitaxy, utilizing growth interruption in the hydrogen/nitrogen atmosphere and variable reactor pressure to control the AR microstructure. Realistic configuration of the QD AR implied in simulations was directly extracted from HRTEM characterization of the grown QD-based structures. Multi-scale 2D simulations of the carrier transport inside the multiple QD AR have revealed a non-trivial pathway for carrier injection into the dots. Electrons and holes are found to penetrate deep into the multi-layer AR through the gaps between individual QDs and get into the dots via their side edges rather than via top and bottom interfaces. This enables a more homogeneous carrier distribution among the dots situated in different layers than among the later...
Superlattice Microstruct, 2007
A model for exciton formation, dissociation and transport is proposed for the simulation of an el... more A model for exciton formation, dissociation and transport is proposed for the simulation of an electrically pumped polariton laser with a geometry similar to that of a VCSEL and resonant cavity LEDs. We demonstrate how the strain effects and the geometry of the device influence the exciton distribution for a GaN/InGaN laser structure.
Superlattice Microstruct, 2007
In the last years GaN-based heterostructures have attracted much attention for their application ... more In the last years GaN-based heterostructures have attracted much attention for their application as optoelectronic devices. The strain due to lattice mismatch of the constituent materials plays a crucial role in the behaviour of these structures, especially if they are of reduced dimensions, as e.g. nanocolumns. We show an implementation of a new device simulator which accounts for strain-related effects and quantum mechanical properties and couples them with the transport of the quasi-particles in the system. Simulations of an AlGaN/GaN nanocolumn LED are reported as an example.
Scientific reports, May 16, 2016
Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for fut... more Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the "OFF" state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only ...
Nano letters, Jan 7, 2016
Metropolis Monte Carlo simulations are used to construct minimal energy configurations by electro... more Metropolis Monte Carlo simulations are used to construct minimal energy configurations by electrostatic coupling of rotating dipoles associated with each unit cell of a perovskite CH3NH3PbI3 crystal. Short-range antiferroelectric order is found, whereas at scales of 8-10 nm, we observe the formation of nanodomains, strongly influencing the electrostatics of the device. The models are coupled to drift-diffusion simulations to study the actual role of nanodomains in the I-V characteristics, especially focusing on charge separation and recombination losses. We demonstrate that holes and electrons separate into different nanodomains following different current pathways. From our analysis we can conclude that even antiferroelectric ordering can ultimately lead to an increase of photoconversion efficiencies thanks to a decrease of trap-assisted recombination losses and the formation of good current percolation patterns along domain edges.
Physical Review Letters, 2016
White light emitting diodes based on III-nitride InGaN/GaN quantum wells currently offer the high... more White light emitting diodes based on III-nitride InGaN/GaN quantum wells currently offer the highest overall efficiency for solid state lighting applications. Although current phosphor-converted white LEDs have high electricity-to-light conversion efficiencies, it has been recently pointed out that the full potential of solid state lighting could be exploited only by color mixing approaches without employing phosphor-based wavelength conversion. Such an approach requires direct emitting LEDs of different colors, in particular in the green/yellow range ov the visible spectrum. This range, however, suffers from a systematic drop in efficiency, known as the "green gap", whose physical origin has not been understood completely so far. In this work we show by atomistic simulations that a consistent part of the "green gap" in c-plane InGaN/GaN based light emitting diodes may be attributed to a decrease in the radiative recombination coefficient with increasing Indium content due to random fluctuations of the Indium concentration naturally present in any InGaN alloy.
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Papers by Matthias Auf der Maur