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Electronic Transport Properties of Skutterudites
Published in Ctirad Uher, Thermoelectric Skutterudites, 2021
An extrinsic semiconductor usually has a larger band gap and contains a number of impurities that can either give off electrons to the conduction band (donors) or accept electrons from the valence band (acceptors). The impurity levels are located in the band gap and can be either fairly close to the respective conduction or valence band edges (shallow impurities) or near the middle of the band gap (deep impurities). The conduction process is determined by the density of the donors (or acceptors), their separation from the conduction (valence) band edge, and the temperature.
Fundamentals of Semiconductor Physics
Published in Samar K. Saha, FinFET Devices for VLSI Circuits and Systems, 2020
An extrinsic semiconductor is a semiconductor material with added elemental impurities called dopants. As we have discussed in Section 2.2.3, the intrinsic semiconductor at room temperature has an extremely low number of free-carrier concentration providing a very low conductivity. Thus, the added impurities introduce additional energy levels in the forbidden gap and can easily be ionized to add either electrons in the CB or holes in the VB, depending on the type of impurities and impurity levels in silicon as discussed below.
Review of Basic Device Physics
Published in Samar K. Saha, Compact Models for Integrated Circuit Design, 2018
An extrinsic semiconductor is a semiconductor material with added elemental impurities called dopants. As we discussed in Section 2.2.3, the intrinsic semiconductor at room temperature has an extremely low number of free-carrier concentration, yielding very low conductivity. The added impurities introduce additional energy levels in the forbidden gap and can easily be ionized to add either electrons to the CB or holes to the VB, depending on the type of impurities and impurity levels.
Electromagnetic bandgaps of fixed-length Thue-Morse plasma/dielectric/superconductor photonic band multilayers
Published in Philosophical Magazine, 2023
Malihe Nejati, Mehdi Solaimani, Sanaz Azizi
Fabrication of photonic crystals is now possible utilizing different methods including sol–gel [17], photo-electrochemical etching of silicon [18], holography [19], two photon phase mask lithography [20], block copolymerization-induced microphase separation [21], inkjet printing [22], etc. In past years, the building blocks in the photonic crystal are produced from different materials, including magnetized ferrites [23], ferrofluids [24, 25], hyperbolic metamaterials [26], epsilon-near-zero metamaterials [27], single-negative materials [28], nonlinear nanocomposite materials [29], graphene [30], metal/dielectric [31], extrinsic semiconductor [32], chalcogenides [33], anodic aluminum oxide [34], liquid crystals [35], x-cut lithium niobate [36], etc. The photonic crystals can be made using different arrangements of the composing layers. Therefore, many researchers have tried to consider different arrangments such as the Dodecanacci sequence [23], Octonacci [37], symmetric quinary photonic crystals [38], Thue – Mosre [6, 39], double-periodic [39], Gaussian random multilayers [32], etc. Also, different concepts in photonic crystals can be addressed such as active control of transmission and group velocity [40], Omnidirectional band gaps [41], Slow light [42], Frozen light [43], electrically-tunable defect modes [44], quantum transmission characteristics [45], Controlling ultrashort pulses shape [46], Fano resonance [34], Ultrashort pulse propagation and nonlinear second harmonic generation [47], gradient refractive index [48], etc.
Surface waves in piezoelectric semiconductor by using Eigen value approach
Published in Waves in Random and Complex Media, 2023
Adnan Jahangir, Sayed M. Abo-Dahab, Aiman Iqbal
Piezoelectric materials are materials that have the ability to create inner electrical charge from applied mechanical stress. Piezo is a Greek word used for ‘push’. A few normally happening substances in nature show the piezoelectric impact. These are DNA, Enamel, Silk, certain ceramics, crystals, Bone, Dentine and many more. The conductivity of semiconductors is in between insulators and good conductors, and it increments with expansion in temperature. A pure semiconductor, accordingly, acts as an insulator. The resistance of a semiconductor decreases with expansion in temperature. In a pure semiconductor, which carries on like an insulator under standard conditions, if modest quantity of certain metallic impurity is added, it achieves current conducting properties. The impure semiconductor is then called ‘impurity semiconductor’ or ‘outward semiconductor’. The way toward adding impurity to a semiconductor to make it extrinsic semiconductor is called Doping.
Thermoelastic interactions in a rotational medium having variable thermal conductivity and diffusivity with gravitational effect
Published in Waves in Random and Complex Media, 2023
Sunil Kumar, Aarti Kadian, Kapil Kumar Kalkal
The thermal conductivity of various solid materials like metals, alloys, semiconductors and ceramics is strongly dependent on the ambient temperature. In case of metals, the combined effect of average thermal energy of electrons and lattice vibrations would decide the thermal conductivity and in most of the cases it decreases with increase in temperature. In case of semiconductors, the number of conduction electrons increases exponentially with temperature, for example, in Si crystal, with every 10 degree increment in temperature results in increment of conduction band electrons by a factor of 2. Hence, the thermal conductivity of intrinsic and extrinsic semiconductor materials is very sensitive to the temperature field [1]. The above-mentioned effects are important for ceramics too, as demonstrated by Godfrey [2]. In his measurements, the temperature variation of ceramics by 400 resulted in a drop of thermal conductivity by 45 percent. On the other hand, diffusivity is strongly related with the concentration of diffusing substance [3,4] and may depend upon the temperature too [5]. Thus it is very important to study the interactions among strain, temperature and concentration field for thermoelastic investigations. For considering such interactions, the coupled theory of thermodiffusion was given by Nowacki [6], which predicts infinite speed of propagation of thermoelastic signals. Sherief et al. [7] established the generalized model of thermodiffusion which ensures finite speed of propagation of thermal and diffusive waves. Later, many other problems [8–10] were studied in which thermal conductivity and diffusivity were assumed as constant. However, the material properties change with variation in temperature and concentration.