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Hall Effect Characterization of Nanowires
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Olof Hultin, Kristian Storm, Lars Samuelson
The current in a semiconductor can be described by drift and diffusion. Drift current is due to the electrons’ response to an electric field, whereas diffusion current is caused by diffusion of carriers between areas with different carrier densities. The drift and diffusion currents for electrons can be written as Jn=qnμE+μkTdndr
Review of Basic Device Physics
Published in Samar K. Saha, Compact Models for Integrated Circuit Design, 2018
The drift of charge carriers under an applied electric field E results in a current, called the drift current. For a homogeneous n-type silicon, if there are n number of electrons per unit volume each carrying a charge q flow with a drift velocity vd, then the electron drift current density is given by () Jn,drift=qnvd=qnμnE
NEGF Method for Design and Simulation Analysis of Nanoscale MOS Devices
Published in Ashish Raman, Deep Shekhar, Naveen Kumar, Sub-Micron Semiconductor Devices, 2022
The flow of electrons in any conductor is classically described by drift and diffusion phenomena. The drift current is caused by an electric field that occurs due to an electrostatic potential gradient. The driving electrochemical potential (µ) across the conductor is a combination of two different potentials, i.e., chemical potential (µ − U) and electrostatic potential (U) [3], as depicted in Figure 12.4.
Asymmetry Switching Behavior of the Binary Memristor
Published in IETE Journal of Research, 2022
Mohammad Saeed Feali, Arash Ahmadi, Mohsen Hayati
Now, we want to determine the reset time of memristor, the time that should be elapsed until memristor changes from LRS to HRS. The transient behavior of vacancy concentration throughout the device after applying +2 V to the B contact is shown in Figure 5. Positive bias pushes away the vacancies from the B contact. Initially, the vacancy moves rapidly, but its velocity reduces over time. Increasing vacancy concentration near the A contact causes increasing the concentration gradient. Hence, the increased diffusion current of vacancies, which flows in the opposite direction of the drift current, leads to reducing the overall velocity of vacancy movement. In this case, the rate of vacancy transport is slower compared to the pervious case when the memristor was changing from HRS to LRS. To explain this, the electric field profile across the memristor during the set and reset operations is shown in Figure 6. As shown in the figure, according to the Poisson’s equation, the evolution of vacancy concentration throughout the device modulates the electric field. Figure 6 shows that as the time elapses during set operation, typically vacancies experience lower electric field. At the primitive times during the set operation, an abrupt change in the profile of vacancy concentration is obvious and it leads to high electric field at where the vacancies are accumulated. At the latter times, vacancy concentration near the B contact increases and leads to change in the electric field profile such that typically electrons experience lower electric field.
A Graphene based bimetallic plasmonic waveguide to increase photorefractive effect
Published in Waves in Random and Complex Media, 2021
Equation (4) is the rate equation for the density of ionized donors. The first term describes the photoionization process of electrons from the donor level. The second term takes into account the recombination of the electrons into traps or ionized donors. Equation (5) is the continuity equation for the electron density. Equation (6) is the Poisson equation for the electric field. It describes the spatially modulated part of the electric field generated by the non-uniform distribution of the charge carriers in the crystal. Equation (7) describes the different contributions to the electron current density. The first term gives the diffusion process of the electrons generated by the electron concentration gradient. The second term describes the drift current in the total electric field. The last term gives the photogalvanic current. The last equation is electrostatic condition.
Single event transient study on PMOS-NMOS cross-coupled LC-VCO using PLL
Published in International Journal of Electronics, 2021
Signal event effects and terrestrial radiation cause reliability issues and affects the performance of sub nanometre CMOS circuits in unpredictable ways. When an energetic radiation particle strikes the drain-bulk junction in PMOS or NMOS transistor, several electron-hole pairs are generated in the junction also along the track length of incident particle. The drift current produce by these free carriers under the electric field generates a single event transient (SET) voltage pulse. In combnational logic; if this pulse propagates and reaches latching window, incorrect data can be stored resulting in single upset (SEU). Storage cells in a digital circuit registers incorrect value due to SEU-induced bit flips leading to increased Soft Error Rate (SER) ((Ferlet-Cavrois et al. (2013); Gadlage et al. (2004); Gill et al. (2009)). On the other hand, SET in analog circuits causes temporary variation in output voltage (Adell et al. (2000). SEU and SET are two major effects caused by heavy ions in a radiation-rich environment such as space, defence and nuclear applications in CMOS circuits.