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Electrons in Semiconductors
Published in Hualin Zhan, Graphene-Electrolyte Interfaces, 2020
It can be concluded from Fig. 2.17c,d that the intrinsic charge carrier density in a semiconductor greatly depends on the bandgap, and the low carrier density of an intrinsic semiconductor is not enough for most applications. A common technique to increase the charge carrier density in semiconductors is to introduce dopants (different elements). These elements create additional D(Ɛ) within the bandgap, and hence shift ƐF.
Introduction to Organic Thermoelectric Materials and Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Suhana Mohd Said, Mohd Faizul Mohd Sabri
In the case of nonchemically or electrode-doped conjugated polymers, polarons hop to the next neutral segment and are unhindered due to the lack of counterions. However, a low charge carrier density results in a low electrical conductivity. Doping introduces additional charge carriers to the polymer chain, which results in the localization of charges in Coulomb traps, due to the electrostatic interaction with the counterions. At low doping concentrations, these trapped charges suppress the mobility of the charges [19]. Increasing the doping concentration will cause the traps to overlap (1017 cm−3), thus reducing the energy barriers associated with the disorder of the pi-orbitals. Thus, an increase in the doping concentration correspondingly increases the charge mobility. For higher doping concentrations up to 30%, low-energy barriers that facilitate charge hopping coupled with high carrier densities enable conductivities of several thousand S cm−1 [12].
A 100-Mrad (Si) JFET-Based Sensing and Communications System for Extreme Nuclear Instrumentation Environments
Published in Nuclear Technology, 2022
F. Kyle Reed, M. Nance Ericson, N. Dianne Bull Ezell, Roger A. Kisner, Lei Zuo, Haifeng Zhang, Robert Flammang
The dielectric constant of a material is proportional to the bound charge carrier density. Because the radiation dose and dose rate unbind these charge carriers into free charge carriers, which increases the material conductivity as shown in Eq. (6), the bound charge carrier density of the material decreases. Therefore, the capacitance, which is proportional to the dielectric constant, varies with inverse proportionality to radiation-induced conductivity. As discussed in Eq. (1) and (2), the frequency of each oscillator is inversely proportional to capacitance, which dominates the observed frequency drift that follows the curve of Eq. (6). Other sources of frequency error can be attributed to variations in the JFET capacitances due to their overlays, increased leakage currents in the transistors and capacitors, increased conductivity of the resistors, and variations in board parasitics.
Opto-electronic characterization of third-generation solar cells
Published in Science and Technology of Advanced Materials, 2018
Martin Neukom, Simon Züfle, Sandra Jenatsch, Beat Ruhstaller
Differential charging combines small-perturbation transient photocurrent (TPC) and transient photovoltage (TPV) measurements. From the two experiments the differential capacitance C = ΔQ/ΔV is calculated for varied light intensity. The integral reveals the charge carrier density at open-circuit [13,63]. The charge ΔQ stems from the current-integral of TPC whereas the ΔV is the change in voltage in TPV. Both experiments are performed with offset-light and a small light pulse.
Variable thermal conductivity during photo-thermoelasticy theory of semiconductor medium induced by laser pulses with hyperbolic two-temperature theory
Published in Waves in Random and Complex Media, 2021
A. M. S. Mahdy, Kh. Lotfy, A. A. El-Bary, E. M. Roshdy, M. M. Abd El-Raouf
When a semiconductor material surface is exposed to a normal laser beam, the net charge carrier density is produced. Following the hyperbolic two-temperature theory [36], the system of equations that describes the coupled plasma, thermal and elastic effects during the excitation transport process are [5,19,45,46]: