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Introduction to Semiconductor Physics
Published in Lev I. Berger, Semiconductor Materials, 2020
Photoconductivity of a substance is the change of its electrical conductivity as a result of absorption of electromagnetic radiation. The absorption of a photon may transfer an electron from the valence to conduction band with simultaneous generation of a hole in the valence band (intrinsic photoconductivity). The extrinsic photoconductivity results in transition of the donor elections to the conduction band or transition of holes from acceptor impurities to the valence band. These elections and/or holes change the conductivity of the crystal which the crystal has at the same temperature without irradiation (dark conductivity).
Detectors
Published in Erich Kasper, Jinzhong Yu, Silicon-Based Photonics, 2020
A photoconductive device realizes the simplest photodetector. It exploits the change in conductivity of a semiconductor that is illuminated. The intrinsic photoconductivity involves the excitation of electrons and holes from a photon absorption process. This process occurs when the energy of the photon exceeds the bandgap energy. The technological realization needs ohmic contacts on both sides of the illuminated area. A voltage bias is applied on these contacts. The current through the device increases under illumination because of the additional carriers caused by absorption. This detector principle functions not only for a single crystalline material but also for polycrystalline or amorphous materials. Therefore, it is frequently used in early phases of material testing when technology is under development.
P
Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
Photoconductivity of the layer depends on its composition, the solvent used, and preparation conditions. Usually the skeleton of photoconductive complex contains helixshaped PVK chains with a low molecular weight sensitizer inside the helix. It is possible to enhance the photoconductivity by doping this system with special additives. Preparing and conditioning of the layer is very important and has great influence on its final properties and stability. The electrophotographic properties of layers obtained from PVK-TNF (trinitrofluorenone) complexes of various molar ratio have been investigated. The molar ratio (moles TNF: monomer units of PVK) varied from 0.2–1.2.
Photoconductivity study of ZnxS1-x thin film using multiple light sources
Published in Phase Transitions, 2022
Kayode Oladele Olumurewa, Saheed Adekunle Adewinbi, Alexandra Adesina Willoughby, Marcus Adebola Eleruja
Semiconductors materials such as ZnO, TiO2 and ZnS have been utilized for varying applications because of their electronic and optical properties. The ability to tune the properties of these semiconductor materials by doping with metals [1–4] has resulted in materials with enhanced properties in opto-electronic applications. Amongst these applications, utilizing semiconductors as photodetectors is important in the opto-electronics industry. Photodetectors are devices that generate an output signal as a result of an illuminated input light source in the active region [5]. During the process of photoconductivity, there is spontaneous conversion of photons of light into an electrical signal due to the mobility of charge carriers [6,7]. When the individual photons are absorbed, it causes a change in the characteristics of the sensor. Typically, the resistance decreases when a material is illuminated, though there are unique cases where resistance increases [8]. Photoconductivity is the result of the absorption of photons of light leading to the formation of charge carriers in the conduction band and/or in the valence band [5,9]. In the process, electron-hole pairs are generated, recombined and transported to the electrodes where photosensing is observed. Photoconductivity gives salient information about the characteristics of materials and applications in photosensing and radiation measurements.
First principles study of the electronic, optical, elastic and thermoelectric properties of Nb2WNi alloy
Published in Molecular Physics, 2021
M. Güler, Ş. Uğur, G. Uğur, E. Güler
The photoconductivity or so-called optical conductivity describes the increasing electrical conductivity when the considered material is exposed to sufficient photon energy. Figure 8 pictures the optical conductivity characteristics of Nb2WNi alloy. The Im (σ2) and Re (σ1) parts of the optical conductivity peak of Nb2WNi alloy begin from zero at the same time. This synchronic beginning denotes the nonexistence of any bandgap at the EF level [26–31]. So, this result once more supports the metallic behaviour of Nb2WNi alloy following the electronic band results. Also, the maximums in the IR region for both crystal structures imply that Nb2WNi alloy can be a promising material for practical applications of solar energy because of its IR conductivity [26–31].