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Fundamentals of TFETs and Their Applications
Published in Balwinder Raj, Ashish Raman, Nanoscale Semiconductors, 2023
V. Ramakrishna, A. Krishna Kumar
General TFET components are made of the same material, so the region where tunneling occurs belongs to the homojunction. The energy gaps on both sides of the junction are equal, and the relative position is adjusted by different doping types and concentrations. A heterojunction is a junction formed by two materials with different energy gap sizes and similar lattice sizes. Figure 2.9 shows the three common alignment methods for heterojunctions. The heterojunctions on the left and right are not suitable for use in TFETs, because the energy band distribution on the left requires a very large gate bias to occur at the junction. In the tunneling mechanism, on the contrary, the gap of the right junction energy gap is too large, which will cause the TFET to turn on without the gate bias, so it is not a suitable shape; only the middle energy band distribution is an ideal state. Since the tunneling probability has a considerable relationship with the position of the energy band distribution, if a suitable material is selected and doped to form a heterogeneous junction, the performance of the TFET can be greatly improved [38, 39].
Planar and Nanostructured Semiconductor Junctions
Published in Juan Bisquert, The Physics of Solar Energy Conversion, 2020
A heterojunction is a junction between crystalline semiconductors that have different bandgaps. Band alignment rules are necessary to predict the properties of heterojunctions. An example is shown in Figure 9.22. This figure shows the significance of the different energy levels that were discussed in Chapter 2: the VL, the conduction band (and valence band) level, and the Fermi level. The difference of the Fermi levels is a built-in potential that has to be transferred at the interface by an equivalent displacement of the VL so that the Fermi level across the junction in equilibrium is flat. In addition to the difference of Fermi levels, the separate materials present an offset of the conduction band levels, obtained by taking the difference between their electron affinities, Δχ. The simplest rule to establish the energetic structure of the heterojunction is the electron affinity rule, in which the initial conduction band offset is preserved (Capasso and Margaritondo, 1987). Neglecting any surface dipoles and charges, the offset of the VL that is established corresponds to band bending in the semiconductors, as indicated in Figure 9.22b.
Metal Oxide Based Heterojunction Nanoscale Materials for Chemiresistive Gas Sensors
Published in Mahmood Aliofkhazraei, Advances in Nanostructured Composites, 2019
Keerthi G. Nair, V.P. Dinesh, P. Biji
Heterojunctions are contacts between two different materials with interesting electrical or electro optical properties. Although a heterojunction, in general, is defined as the physical interface between two dissimilar materials, its usage in semiconductor research is normally restricted to a junction between two different monocrystalline semiconductor materials. Such heterojunctions can be classified as abrupt or graded according to the distance during which the transition from one material to the other is ended up across the interface. In the former case, the transition occurs within few atomic distances (< 1 μm), while in the latter, it takes place over distances of the order of several diffusion lengths. Another classification, which is often used in literature, involves naming the heterojunction by the type of conductivity present on both regions of the junction. If both semiconductors concerned have related types of conductivity, the junction is described as isotype heterojunction, otherwise it is termed as anisotype heterojunction.
Gamma-Induced Degradation Effect of InP HBTs Studied by Keysight Model
Published in Nuclear Science and Engineering, 2021
Jincan Zhang, Lei Cao, Min Liu, Bo Liu, Lin Cheng
With a large band gap material for the emitter layer, heterojunction bipolar transistors (HBTs) fabricated by either molecular beam epitaxy or metal organic chemical vapor deposition growth techniques are often used in communication systems of military and commercial space satellites.1,2 These devices not only have superior electronics transport properties but also offer higher radiation hardness as compared to Si-based devices. On the basis of indium phosphide (InP)/indium gallium arsenide (InGaAs) and indium aluminum arsenide (InAlAs)/InP heterojunctions, HBT lattices matched to InP substrates have received considerable use in many high-speed analog, digital, and mixed signal applications. Additionally, the high radiation hardness of InP HBTs is an important consideration for radiation environment applications.3–5
Modification strategies of TiO2 for potential applications in photocatalysis: a critical review
Published in Green Chemistry Letters and Reviews, 2018
M. Humayun, F. Raziq, A. Khan, W. Luo
In semiconductors-TiO2 heterojunctions, both the components can be excited by photons to generate charge carriers (electron–hole pairs). The charge transfer direction would mainly depend on the relative VB and CB position of both semiconductors. Primarily, the heterojunctions between TiO2 and other semiconductors are categorized into three types as shown in Figure 14. In Type-I heterojunction, the two semiconductors should be either n-type or p-type. Suppose the two semiconductors are represented by A and B. The CB of B should be higher and its valance band should be lower than that of A. Therefore, both the electrons and holes would transfer to semiconductor A. In type-II heterojunctions, the photogenerated electrons would transfer from B to A, while the photogenerated holes would transfer from A to B. Such type of heterojunction is much beneficial, because of the effectively separation of electron–hole pairs. Type-III heterojunction is similar to type-II except for the more prominent difference in VB and CB positions, which requires a huge driving force for photogenerated charge transfer.
CdIn2S4-based advanced composite materials: Structure, properties, and applications in environment and energy – A concise review
Published in Inorganic and Nano-Metal Chemistry, 2023
Gaurav Yadav, Md. Ahmaruzzaman
A heterojunction is an interface between two dissimilar semiconductors. And the combination of several heterojunctions is termed heterostructure. Construction of heterojunction,[38] especially p-n junction,[39,40] is an effective way to enhance photocatalytic activity,[41,42] which enhances the stability of photocatalysts as well as accelerating charge carriers.[43] Usually, heterostructures are obtained by the solid-state method through coupling.