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Graphene-Based Detectors
Published in Antoni Rogalski, 2D Materials for Infrared and Terahertz Detectors, 2020
Photodiodes are usually operated at zero bias (photovoltaic mode) or at reverse bias (photoconductive mode). The absolute response of the photodiode is usually smaller than that of a photodetector working with the photoconducting or photogating mechanisms, since there is no internal gain. Under the reverse-bias operation, the junction capacity is reduced, increasing the speed of the photodiode. Strong reverse bias can initiate impact ionization multiplication of carriers, or avalanching (avalanche photodiode). The large internal gain results in detection of an extremely low signal power. Electron-electron scattering in graphene can lead to the conversion of one high electron-hole pair (e-h) energy into multiple e-h pairs of lower energy, potentially enhancing the photodetection efficiency [6].
Leakage Currents in FinFETs
Published in Samar K. Saha, FinFET Devices for VLSI Circuits and Systems, 2020
Impact ionization is a physical phenomenon of ionizing the lattice atoms by highly energetic electrons knocking out VB electrons from the lattice atoms creating electrons and holes. Thus, when nFinFET devices operate in the strong inversion regime, the channel electron traveling through high electric field near the drain end of the channel can become highly energetic. These highly energetic electrons are called hot electrons. These hot electrons with sufficient kinetic energy, when they collide with the lattice atoms, can ionize the lattice atoms by knocking out electrons from the VB leaving behind holes [7–10]. The holes go into the substrate creating substrate leakage current Isub as shown in Figure 7.4. Some of the electrons have enough energy to overcome the Si/SiO2 energy barrier to reach the gate oxide and generate gate current Ig as shown in Figure 7.4. And, some are collected to the drain contributing to the drain current Ids. The maximum electric field Em near the drain has the greatest control of hot-carrier effects.
GaN-Based Schottky Barriers for Low Turn-On Voltage Rectifiers
Published in Krzysztof Iniewski, Santosh K. Kurinec, Sumeet Walia, Energy Efficient Computing & Electronics, 2019
Nishant Darvekar, Santosh K. Kurinec
High breakdown voltage is achieved by increasing the distance between the anode and cathode and growing thick layers of semiconductors with low concentration of carriers. On the other hand, these parameters increase Ron. Thus, there always has to be a trade-off between these two terms to meet the required Figure of Merit (FOM). Impact ionisation is the reason for avalanche breakdown in power electronic devices. Methods for edge termination, like ring gaurds and field plates, are used in devices. Field plate engineering is commonly performed to enhance the performance of the device in reverse bias mode by extending the depletion region even further. The incorporation of a field plate has known to increase the breakdown voltage up to 5 times for similar device geometries [46]. The length of the field plate along with the nitride passivation play an important role in dictating breakdown voltages. The nitride film should be thick enough to sustain a high electric field without breaking down and thin enough for the electric field to influence the 2DEG. Thus, optimum nitride passivation thickness and field plate length needs to be chosen [47]. A magnesium-doped buried layer or a carbon doped barrier in the GaN channel also improves the breakdown characteristics [42,46]. The breakdown is also directly related to the diameter of the Schottky contact. Circular contacts help weaken the electric field at the periphery.
A Simulation Approach for Depletion and Enhancement Mode in β-Ga2O3 MOSFET
Published in IETE Technical Review, 2022
Pharyanshu Kachhawa, Nidhi Chaturvedi
Temperature-dependent mobility model for mobility and BOLTZAMAN statistics for carrier transport is being considered for simulation. Self-heating effects are considered by incorporating LAT.TEMP lattice thermal models and solving heat flow equations. Low-field temperature-dependent mobility is taken using Equation (1) with TMUN=2.0 [17]. where TL is lattice temperature and µn0 is low-field mobility. In addition to this for high-field saturation, field-dependent mobility model FLDMOB is used for which electron saturation velocity is considered as 1.8 × 107 cm/s [2]. The built-in impact ionization model is also included to analyze the impact ionization in the structure; therefore, breakdown voltage is calculated. The ionization coefficient α based on the Chynoweth model is given by where a = 7.9×105/cm and b = 2.92 × 107 V/cm [18]. These exact values are considered in the simulations without any modifications. The simulation physical model parameters are calibrated and compared with the experimental data [12] to validate the simulation results. All the relevant plots are shown in Figure 2.
Ka band noise comparison for Si, Ge, GaAs, InP, WzGaN, 4H-SiC-based IMPATT diode
Published in International Journal of Electronics Letters, 2019
Girish Chandra Ghivela, Joydeep Sengupta, Monojit Mitra
Due to the random variation of impact ionisation process, there are disturbances in the electric field, voltage and current distributions through the diode. These fluctuations are assumed as the constituent of shot noise current fluctuation due to avalanching multiplication process and considered as small signal in nature (Dash, Mishra, & Panda, 1996; Mishra, Dash, Pattanaik, & Mishra, 2004). Since the noise affects the amplification of microwave signals, it is important to study the effect of noise, and its characteristic along the diode structure is computed using the simulation program in our analysis (Mishra, Panda, & Dash, 1997; Panda, Pavlidis, & Alekseev, 2001; Reklaitis & Reggiani, 2005). The noise characteristics like noise spectral density, i.e. mean square noise voltage (MSNV) per bandwidth (V2/df) and noise measures (NMs) of the diode are computed from this analysis. Let be the noise generation rate at (position of noise source) in the generation region resulting into deviation of mean square noise current over a small frequency interval of df as given in Equation (6).
Validation and Verification of the Evaluated Electron Data Library in FRENSIE
Published in Nuclear Science and Engineering, 2019
Luke J. Kersting, Douglass Henderson, Alex Robinson, Eli Moll
In an electroionization or impact ionization reaction, an electron interacts with an atomic electron that results in the ionization of the target atom and the production of a knock-on electron (delta ray). The primary electron and the knock-on electron are indistinguishable, and it is assumed that the lower-energy electron is the knock-on electron. The maximum energy of the knock-on electron is given as