China
Africa
Explore chapters and articles related to this topic
Semiconductor Heterojunctions, Modulation-Doped Quantum Wells, and Superlattices
Published in Jyoti Prasad Banerjee, Suranjana Banerjee, Physics of Semiconductors and Nanostructures, 2019
Jyoti Prasad Banerjee, Suranjana Banerjee
The electrons associated with the donors in AlGaAs lie in energy levels higher than those of subband energy levels in the quantum well formed in the narrow gap material GaAs. Naturally those electrons drop down to the lowest subband energy state (εl) in the well. The positively charged donors in the donor level and electrons spilled over from the donor atoms to the subband quantized energy level are thus spatially separated. This spatial separation of positively charged donor atoms and negatively charged electrons creates a dipole layer due to which a built-in electric field is created. This electric field causes band bending and forms a triangular quantum well (Figure 6.6b) in which the electrons are trapped in the subband energy level. The electric field profile can be obtained from the solution of Poisson’s equation. The quantum well is triangular in shape, and the electrons in this well form a 2-DEG that is free to move in the plane of a heterointerface. The electron motion is quantized in a direction perpendicular to this plane, which is the plane of epitaxial growth. The spatial separation of electrons and ionized donors reduces their Coulomb interaction potential and decreases the rate of electron scattering by the ionized impurities to a minimum. Thus both carrier relaxation time and mean free path for impurity scattering increase. This leads to an increase of mobility of electrons for their motion along the heterointerface (x, y) plane. Modulation doping therefore leads to high electron mobility.
The Junctionless Transistor
Published in Simon Deleonibus, Emerging Devices for Low-Power and High-Performance Nanosystems, 2018
Finally, a study by Ueda et al. based on atomistic sp3d5s* tight-binding simulations of heavily doped junctionless GAA silicon nanowire transistors shows that if the doping atoms can be periodically placed along the channel length, high bulk values mobility values can be obtained [47]. The evenly spaced doping atoms form periodic potential wells for the majority carriers, which can easily tunnel from one impurity well to the next. Placing doping atoms in an evenly distributed manner constitutes an important challenge for device processing, but it can be achieved [46]. An increase of doping concentration increases the transmission of carriers from source to drain, such that electron mobility can in principle increase from 50 to 300 cm2V−1s−1 when the doping concentration is increased from 2 × 1019 to 8 × 1019 cm−3, respectively [47].
Electrical Behavior
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
A major factor that affects electron mobility is temperature. Increasing temperature produces thermal vibrations that have a scattering effect which reduces the mean free path. As a result, the electronic conductivity of metals decreases (and the electrical resistivity, reciprocally, increases) as the temperature increases. Resistivity vs. temperature is shown in Figure 10.3 for some metals.
Mechanical reliability, thermal stability and thermoelectric performance of the transition-metal nitride CrN
Published in Philosophical Magazine Letters, 2020
Jing Jiang, Junfeng Xia, Ting Zhou, Yi Niu, Yide Chen, Jun Luo, Jing Liu, Jiawei Zhou, Jiahao Fan, Chao Wang
The thermoelectric performance of bulk CrN sample is summarised in Figure 5. As shown in Figure 5a, the electrical conductivity decreases with increasing temperature, indicating a metal-like transport behaviour. The CrN we have prepared in this study has an excellent electrical conductivity as high as 1195 S cm−1 at 348 K. This is nearly 60 times larger than the previously reported value in bulk CrN sample [12]. The enhanced electrical conductivity results from an increase in both the electron mobility and the carrier concentration. As illustrated in Table 2, the results of room-temperature Hall effect measurement show that the carrier concentration in the sample is 4.61 × 1020 cm−3, which is more than one order of magnitude higher than that reported previously (4.1 × 1019 cm−3), and the mobility μ = 16.17 cm2 v−1 s−1 is also more than 10 times larger than previously reported one (μ = 1.5 cm2 v−1 s−1) [13].
Demonstration of Temperature-Dependent Analysis of GAA – β-(AlGa)2O3/Ga2O3 High Electron Mobility Transistor
Published in IETE Journal of Research, 2022
Ravi Ranjan, Nitesh Kashyap, Ashish Raman
The electron velocity of the proposed device across the channel is given in Figure 3(c). The drift velocity of the device is directly proportional to electron mobility, and it reduces with an increase in temperature. Figure 3(d) and 3(e) are the plots of drain current in linear and log scale, respectively, with an increase in temperature. Due to larger electron mobility at a lower temperature, the drain current is larger. ION is 750 mA/mm and 150 mA/mm at 50 and 300 K, respectively. The OFF-state current is too low, and it is in the order of 10−11 (A/µm). The GAA structure is used to increase the ION/IOFF ratio.