Conventional Mobility Model Research Articles

Carrier Density Dependence of the Mobility in Disordered Organic Semiconductors with Gaussian Disorder

In this paper, the charge transport properties and energetic disorder are studied for pristine Si-PCPDTBT, mono-PCBM, bis-PCBM, and their blends of Si-PCPDTBT:mono-PCBM, Si-PCPDTBT:bis-PCBM. We show that the current density versus voltage curves of electron-only devices for mono-PCBM, bis-PCBM, Si-PCPDTBT:mono-PCBM, Si-PCPDTBT:bis-PCBM, and hole-only devices for Si-PCPDTBT, Si-PCPDTBT:mono-PCBM, Si-PCPDTBT:bis-PCBM cannot be accurately described using a conventional mobility model within which the mobility depends only on the electric field, but that a fully consistent description of all curves can be obtained using the improved extended Gaussian disorder model (IEGDM). Within the IEGDM, the presence of energetic disorder is described by a Gaussian density of states, and the mobility depends on the electric field and carrier density. Furthermore, we found that the mobility increases as the width of the Gaussian density of states decreases for both electron-only and hole-only devices, and the mobility is closely related to the energetic disorder. We view this as an indication that the energetic disorder appears to govern the charge transport in disordered organic semiconductors.

Enhancing Mobility Based on Realistic Models for Vehicular Ad Hoc Networks

Creation and maintaining of the one-to-one communication link between the nodes in Vehicular Adhoc Networks are challenging. The model which is very much efficient for one particular scenario will not work at the same level of efficiency for another environment. The mobility of the nodes in the network plays a crucial role in establishing a reliable communication model in the VANETs. Analyzing the nature of mobility inside a particular network based on logical and historical data paves an efficient way in the routing of packets by predicting the best route and improve the quality of the network, reliability, and other performance in terms of serviceability. This paper aims to analyze the drawbacks of existing mobility models utilizing various network quality parameters by classifying them into microscopic and macroscopic mobility models. With the insight gained from the analysis, we propose two methodologies where the realistic model for the VANETs can be established. The models are architected with the help of the information provided by the Geographic information system. The conventional mobility models include excessive details such as road and street layouts, intersection with traffic signals, acceleration and deceleration, building, and other obstacles in a realistic mobility model, that requires prolonged time to design and optimize, it should complicate the simulation. Designing an effective, realistic mobility model is crucial. The key objectives of this proposal are to architect realistic VANETs mobility models by taking into account the real-time road environment and actual data according to the traffic demand and improving the real-time performance of VANETs

Carrier transport properties in inversion layer of Si-face 4H–SiC MOSFET with nitrided oxide

We propose a method to evaluate the carrier transport properties in the inversion layer of 4H–SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) experimentally. Our approach differs from conventional methods, which have adjusted the parameters in conventional mobility models. Intrinsic phonon-limited mobility (μphonon) in the SiC MOSFET was observed by suppressing the severe impact of Coulomb scattering on the SiC MOS inversion layer by lowering the acceptor concentration (NA) of the p-type well region to the order of 1014 cm−3. In this study, we investigated the carrier transport properties in the inversion layer of Si-face 4H–SiC MOSFETs with nitrided oxide. It is revealed that the μphonon of the SiC MOSFET is a quarter or less than the conventionally presumed values. Additionally, surface roughness scattering is found not to be the most dominant mobility-limiting factor even at high effective normal field (Eeff) for the SiC MOSFET. These results demonstrate that conventional understanding of carrier scattering in the SiC MOS inversion layer should be modified, especially in the high Eeff region.

Interplay between urban communities and human‐crowd mobility: A study using contributed geospatial data sources

AbstractAn intense process of urbanization, witnessed particularly in the last decade, has stressed the need to comprehend human mobility behavior in urban settings. Although the emergence of contributed geospatial data (i.e., pervasive activity‐based data) has contributed to substantial progress toward understanding human activity, the relationship between human‐crowd mobility and the functional structure of a city is not yet well understood. In this context, the present research focuses on the intra‐urban origin–destination matrix modeling founded on a combination of two major crowdsourced datasets as well as the inclusion of urban communities’ structure. Specifically, the well‐known “radiation” and “PWO” models were modified through first, identifying the communities embedded in the cyberspace network then employing the identified hierarchical structure of the spatial‐interaction network for the formulation of the users’ movement network and second, imposing proper input variables including the telecommunication activity volume and check‐in frequency. The results obtained by various empirical analyses suggest that the modified community‐constrained origin–destination flow estimation models exhibit better performance levels than those of alternative conventional mobility models.

Characterization of the Hole Transport and Electrical Properties in the Small-Molecule Organic Semiconductors

In this paper, we investigate the hole transport and electrical properties in a small-molecule organic material N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB), which is frequently used in organic light-emitting diodes. It is shown that the thickness-dependent current density versus voltage (J–V) characteristics of sandwich-type NPB-based hole-only devices cannot be described well using the conventional mobility model without carrier density or electric field dependence. However, a consistent and excellent description of the thickness-dependent and temperature-dependent J–V characteristics of NPB hole-only devices can be obtained with a single set of parameters by using our recently introduced improved model that take into account the temperature, carrier density, and electric field dependence of the mobility. For the small-molecule organic semiconductor studied, we find that the width of the Gaussian distribution of density of states σ and the lattice constant a are similar to the values reported for conjugated polymers. Furthermore, we show that the boundary carrier density has an important effect on the J–V characteristics. Both the maximum of carrier density and the minimum of electric field appear near the interface of NPB hole-only devices.

Characterization of asymmetric electron and hole transport in a high-mobility semiconducting polymer

The electron and hole transport properties in a high-mobility n-type copolymer poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diy1]-alt-5,5′-(2,2′-dithiophene)}[P(NDI2OD-T2), PolyeraActivInk™ N2200] are investigated. The electron mobility is observed to be more than two orders of magnitude higher than the hole mobility. The thickness-dependent current density versus voltage (J–V) characteristics of N2200 electron-only and hole-only devices cannot be well described using the conventional mobility model. However, the thickness-dependent and temperature-dependent J–V characteristics of N2200 electron-only and hole-only devices can be accurately described using our recently introduced improved mobility model only with a single set of parameters. Within the improved model, the mobility depends on three important physical quantities: the temperature, carrier density, and electric field. For the semiconducting polymer studied, we find the width of the Gaussian density of states σ = 0.082 eV and the lattice constant a = 0.8 nm for electron transport, while the width of the Gaussian density of states σ = 0.11 eV and the lattice constant a = 0.8 nm for hole transport. It is clear that hole transport exhibits a significantly stronger disorder than electron transport. This is also reflected in the lower hole mobility, as compared to the electron mobility.

Measurement of net dopant concentration via dynamic photoluminescence

This paper presents a class of methods to determine net dopant concentration of silicon wafers by means of dynamic or quasi-steady-state photoluminescence. In contrast to resistivity measurements, this approach is independent of assumptions about dopant type and majority carrier mobility. The latter fact makes it particularly interesting for the determination of net dopant concentration in compensated silicon, where conventional mobility models involving only one dopant species have been reported to fail. Our approach also allows access to majority carrier mobility via combination of net dopant concentration as inferred from photoluminescence with a resistivity measurement.

Mobility analysis of surface roughness scattering in FinFET devices

This paper presents a mobility analysis of the surface roughness scattering along the different interfaces of FinFET devices. Using temperature dependent analysis of effective mobility, quantitative information about the influence of the roughness could be obtained directly on the device. The sidewall and top surface drain current components were estimated from the total drain currents of different fin width conditions. Using a conventional mobility model, it was possible to fit the gate voltage and temperature dependence of sidewall and top surface mobilities. This procedure allowed the contribution of the surface roughness scattering to be quantified with nondestructive characterization. Significant differences were observed for sidewalls and top surface. In the specific case under study, surface roughness scattering on sidewalls was about three times stronger than on top surface for n-channel FinFETs, whereas it remained similar for p-channel ones.

Performance evaluation of routing protocols in vehicular ad hoc networks

Vehicular ad hoc network (VANET) is an emerging new class of mobile ad hoc networks, which can be used to improve road safety and comfort of the passengers inside vehicles. Due to mobility constraints and high dynamics, routing is a more challenging task in VANETs. In this work, we evaluate the performance of the conventional ad hoc routing protocols in vehicular network environment. The objective of this study is to assess the applicability of these protocols in different vehicular scenarios. Two location-based and two topology-based ad hoc routing protocols are evaluated in city and highway scenarios. Mobility model has significant effects on the simulation results. Conventional mobility models are unsuitable for VANET simulations. We used intelligent driver model based tool VanetMobiSim to generate realistic mobility traces. Performance metrics such as packet delivery ratio, normalised routing load, end-to-end delay, and throughput are evaluated using NS2.

Hole transport in the organic small molecule material α-NPD: evidence for the presence of correlated disorder

In this paper the hole mobility in the amorphous small molecule material N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (α-NPD), which is frequently used in organic light-emitting diodes, is studied. From an analysis of the temperature and layer thickness dependence of the steady-state current density in sandwich-type α-NPD-based hole-only devices, it is found that a conventional mobility model assuming a Poole–Frenkel type field dependence and neglecting the carrier density dependence is not appropriate. Consistent descriptions with equal quality are obtained within the framework of two forms of the Gaussian disorder model (GDM and CDM), within which the presence of energetic disorder is described by a Gaussian density of states and within which spatial correlations between the site energies are absent or are included, respectively. Both models contain a carrier density dependence of the mobility. Based on a comparison of the site densities as obtained from both models with the molecular density, we argue that the analysis provides evidence for the presence of correlated disorder.

Mobility Modeling in Mobile Ad Hoc Networks with Environment-Aware

Simulation is the most important and widely used method in the research of Mobile Ad hoc NETworks (MANET). The topology of MANET and the mobility of mobile nodes are the key factors that have an impact on the performance of protocols. However, most of the existing works are based on random movement and the fact that the network topology is highly related to the environment of MANET is overlooked. In this paper, we propose a novel Environment-Aware Mobility (EAM) model which models a more realistic movement of mobile nodes. Environment objects such as Route and Hotspot are introduced to represent the environment components which are rendered by Scalable Vector Graphics (SVG). It is considered to be a complex model with a combination of existing conventional mobility models and network environments. This paper shows that various MANET environments can be modeled based on this work. A sample environment is also simulated and the results show that the intrinsic characteristics and properties of the environments have a significant influence on the performance of MANET protocols.