China
Africa
Explore chapters and articles related to this topic
Gan-Hemt Scaling Technologies For High Frequency Radio Frequency And Mixed Signal Applications
Published in Farid Medjdoub, Krzysztof Iniewski, Gallium Nitride (GaN), 2017
Table 4.1 summarizes material properties of commonly used microwave semiconductors, showing advantages of GaN-based material system for high-frequency and high-power applications. III-N semiconductors, with a wide range of band-gap energy varying from 0.7 eV (InN) to 3.4 eV (GaN) to 6.1 eV (AlN), and availability of their ternary (AlGaN, InAlN) and quaternary (InAlGaN) alloys enable flexible design of heterostructures. HEMT epitaxial structures based on III-N heterostructures typically consist of a wide band-gap top barrier material such as AlGaN or InAlN and a GaN channel layer. A high-density two-dimensional electron gas (2DEG) is induced at an interface through spontaneous and piezoelectric polarization effects without a need for intentional doping [8]. A large conduction band offset between the AlGaN (or InAlN) barrier layer and the GaN channel layer effectively increases electron confinement in the channel. The high 2DEG density of 1-2 × 1013 cm–2 combined with their high electron mobility in the range of 1500–2000 cm2/V·s leads to a low channel sheet resistance, resulting in exceptionally low device on-resistance. The high saturation velocity enables not only high current densities leading to a high output power density but also high-frequency operation. Owing to the high critical electric field of GaN, which is >10× higher than Si, AlGaN/GaN HEMTs possesses high breakdown voltage, which allows a large drain bias voltage, leading to a high-power density with a high output impedance per unit RF power. This results in easier matching and lower loss matching circuits. In addition to the unique electrical properties of GaN-based material system, availability of semi-insulating 4H- and 6H-SiC substrates with high thermal conductivity greatly helps to spread heat generated by self-heating during high-power operation, allowing transistors to operate at high-power densities and high efficiency while reducing the requirement for cooling.
Heterostructure Bipolar Transistors
Published in Mike Golio, RF and Microwave Semiconductor Device Handbook, 2017
∈s is the dielectric constant of the semiconductor; Nd and Na are the donor and acceptor doping levels, respectively; and n and p are the mobile electron and hole carrier concentrations, respectively. We apply this equation to the base-collector junction of HBTs, which is typically a homojunction. Since the base doping greatly exceeds the collector doping, most of the depletion region of the base-collector junction is at the collector side. In the depleted collector region where it is doped n-type, Nd in Eq. (5.9) is the collector doping level, Ncoll, and Na is 0. The collector current flowing through the junction consists of electrons. If the field inside the depletion region was small, then these electrons would move at a speed equal to the product of the mobility and the electric field: μn·ε. It is a fundamental semiconductor property that, once the electric field exceeds a certain critical value (εcrit ~ 103 V/cm for GaAs), the carrier travels at a constant velocity called the saturation velocity (vsat). Because the electric field inside most of the depletion region exceeds 104 V/cm, practically all of these electrons travel at a constant speed of vsat. The electron carrier concentration inside the collector can be related to the collector current density (JC; equal to IC/Aemit) as: n(x)=Jcqνsat=constant inside the base-collector junction
Silicon Nanowire Field Effect Transistor Modeling
Published in Razali Ismail, Mohammad Taghi Ahmadi, Sohail Anwar, Advanced Nanoelectronics, 2018
Amir Hossein Fallahpour, Mohammad Taghi Ahmadi
In order to achieve downscaling of devices such as FETs, the emergence of new structures and materials is required. Nanowire is one of the candidates with which FETs can be scaled down. There are a number of high-field transport theories used to answer interdependence, including Monte Carlo simulations, energy-balance theories, path integral methods, Green’s function, and many others. No clear consensus has emerged on the true nature of saturation velocity and its dependence on band structure parameters, doping profiles, or ambient temperature. The presented model based on quantum confinement and high electric field effect illustrates the velocity approach to the modeling of a p-type silicon nanowire transistor. With the development of devices in nanoscale dimensions, the significance of saturation velocity is highlighted. In this work, we extended the work of Arora to embrace the degenerate domain in a p-type nanowire, where in one direction, carriers have analog-typed classical spectrum, while in the other two directions, there is quantum confined or digital spectrum. This work intends to develop a physical model based on SiNWFETs device physics, which can be applied to device behavior in order to explore device matters. The results obtained are applied to the modeling of the current–voltage characteristics of a p-type SiNWFET and finally compared with published data for validation of presented model. Besides this, in this work, we use OMEN for simulation of p-type SiNWFET to compare the I-V characteristics of the simulation result with those of the presented model. The limitations on carrier (holes) drift due to high-field streamlining are also reported. Asymmetrical distribution function that adapts randomness in a zero-field to a streamlined one in a high electric field is employed, where the saturation velocity is always ballistic and the ultimate drift velocity is found to be dependent on thermal velocity for nondegenerately doped nanostructure. However, the ultimate drift velocity is the Fermi velocity for degenerately doped nanostructures. The transport mechanism is presented and applied to the modeling of a p-type SiNWFET. The comparison with the experimental data [49] is not perfect due to the experimental geometry that is not either fully circular or fully rectangular. This prescribed model is very useful in predicting the ballistic nature of an SiNWFET. It is found that in a nanowire channel, the channel conductance is nonzero. Hence, CLM due to the pinch-off point moving in the channel is a mistaken identity that does not exist either for the long or the short channel. Thus, it can be concluded that an infinite electric field is not attainable in the drain end of an SiNWFET device, which concurs with what many researchers have assumed.
Comparative Analysis of Single Event Transients in InGaAs-OI/Bulk/BOI FinFETs for SET-Tolerant InGaAs/Ge-OI Complementary FinFET Circuits
Published in IETE Journal of Research, 2023
The radiation-induced soft errors are serious reliability threats for digital integrated circuits designed to use in radiation environment [1–8,10–13]. The integrated circuits with sub-50 nm technology are more sensitive to these single event transients [14]. The capture rate of the radiation-induced soft errors is more in high-speed integrated circuits due to the increased frequency of operation [15,16]. The replacement of silicon in the channel of MOSFETs with III–V materials such as InGaAs provides better performance due to its increased carrier mobility and saturation velocity [17,18]. The InGaAs and Ge complementary FinFET (C-FinFET) technology is a promising candidate for the next-generation VLSI circuits [18–24]. The SET effect in InGaAs/Ge C-FinFET is dominated by the transients in InGaAs FinFETs due to its high charge collection efficiency, low ionization energy and high mass density [25].
Investigation of RF and DC Performance of E-Mode In0.80Ga0.20As/InAs/In0.80Ga0.20as Channel based DG-HEMTs for Future Submillimetre Wave and THz Applications
Published in IETE Journal of Research, 2021
J. Ajayan, T. Ravichandran, P. Mohankumar, P. Prajoon, J. Charles Pravin, D. Nirmal
The variables T, K, NC, EFn,EC, m, h, γ and n represents the temperature (300 K), Boltzmann constant (1.3807 × 10−23 J/K), conduction band effective density of states, Fermi level electron energy, conduction band, density of states mass, Planck’s constant (6.626 × 10−34 J-Seconds), fitting factor and electron density respectively. Also, the high field electron mobility model adopted for simulation is given by the Equation (3) [34]. where F, µlow, E0 and Vsat represents the driving field strength, low field mobility of electrons, reference field strength and drift electron saturation velocity respectively.
Analytical modelling and electrical characterisation of ZnO based HEMTs
Published in International Journal of Electronics, 2019
Yogesh Kumar Verma, Varun Mishra, Prateek Kishor Verma, Santosh Kumar Gupta
where v is electron velocity, vsat is electron saturation velocity, Fx and Fs are the magnitudes of the electric field and critical electric field, respectively, and µ is the mobility of electrons. The drain current in the linear region is calculated by multiplying electron charge q, 2DEG density ns, width of the channel W, and electron velocity v (El-Banna, 1999). Using (14), and substituting for electric field Fx as negative of potential gradient, and integrating the resultant expression from the voltage VS at source terminal to voltage VD at drain terminal; the expression of drain current (mA\mm) is calculated in terms of the applied gate voltage VG and applied drain voltage VD; while assuming source voltage VS to be zero.