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Analytical Modeling of High Electron Mobility Transistors
Published in D. Nirmal, J. Ajayan, Handbook for III-V High Electron Mobility Transistor Technologies, 2019
A two-dimensional electron gas (2DEG) is a sheet of electrons free to move in two dimensions, but tightly confined in the third. This tight confinement leads to quantized energy levels for motion in that direction, which can then be ignored for most problems. Thus the electrons appear to be a 2D sheet embedded in a 3D world. The analogous construct of holes is called a two-dimensional hole gas (2DHG), and such systems have many useful and interesting properties. Most 2DEGs are found in transistor-like structures made from semiconductors. The most commonly encountered 2DEG is the layer of electrons found in MOSFETs. When the transistor is in inversion mode, the electrons underneath the gate oxide are confined to the semiconductor-oxide interface, and thus occupy well defined energy levels. Nearly always, only the lowest level is occupied, and so the motion of the electrons perpendicular to the interface can be ignored. However, the electron is free to move parallel to the interface, and so is quasi two-dimensional.
Nanotechnology Applications in Electron Devices
Published in Sunipa Roy, Chandan Kumar Ghosh, Chandan Kumar Sarkar, Nanotechnology, 2017
Sarosij Adak, Arghyadeep Sarkar, Sanjit Kumar Swain, Sunipa Roy, Chandan Kumar Ghosh, Chandan Kumar Sarkar
From the new channel material perspective, high-mobility III–V semiconductors having significant transport advantages are extensively being researched as alternative channel materials for upcoming highly scaled devices. The III–V compound semiconductor binaries such as GaAs, GaN, and InP; ternaries such as InGaAs, AlGaAs, AlGaN, and AIInN; and quaternaries such as InAlGaN, InAlGaAs, and GaInPAs are widely studied for enhancing device performance. The GaAs-based compounds have much higher mobility than the silicon-based ones, and they are thus suitable for high-speed operations. On the other hand, III-nitride compounds have a higher bandgap than that of silicon, enabling wide-temperature, high-power, and high-frequency operations. The III-nitride compounds also offer higher breakdown voltage. The heterostructure devices using III–V compound semiconductors consist of two or more layers of different bandgaps grown one above the other. Such heterostructure leads to the formation of a high-mobility quantum well at the heterointerface of the wide-bandgap and the narrow-bandgap semiconductor layers. Hence, charge carriers confined in these quantum wells can move only in two dimensions (2D) and have very high mobility, and they are thus termed two-dimensional electron gas (2DEG).
Entrepreneurship in Power Semiconductor Devices
Published in R. Krishnan, Entrepreneurship in Power Semiconductor Devices, Power Electronics, and Electric Machines and Drive Systems, 2020
A high electron mobility transistor (HEMT) and also known as GaN FET, shown in its basic lateral structure in Figure 4.1 is considered. A very thin layer of aluminum GaN (AlGaN) is grown on top of GaN material. The stress of AlGaN creates a path for high electron mobility between the source (S) and drain (D) when the gate (G) is at zero potential as the threshold of this material combination is zero or slightly negative voltage and a voltage is applied between the drain and source with the drain being positive than the source. The flow of electrons is on the surface and it is termed as two-dimensional electron gas (2DEG). As the source and drain are on the 2DEG itself, it serves to short them with the result that there is a current flow between them. In order to turn off the current from drain to source, the gate voltage is made negative in comparison to both source as well as drain with the result that electrons are depleted and conduction of drain to source current ceases. This type of HEMT is termed as Depletion mode GaN FET. This device is Normally ON at the time of the starting with no bias on the gate and that is not desirable in power conversion applications. In order to keep it nonconducting at the time of circuit startup, a negative voltage has to be applied to the gate and such a constraint in its use is not favorably looked upon also. Users of the power devices are quite used to operation with normally-off condition guaranteed by the silicon device at the time of starting of the circuit/application. Two approaches overcome this disadvantage in the D-mode GaN FET and they are described in the following sections.
Design of 30 nm multi-finger gate GaN HEMT for high frequency device
Published in International Journal of Electronics, 2023
Lijun He, Boyang Zhao, Kang Ma, Chengyun He, Zhiyang Xie, Xing Long, Chaopeng Zhang, Liang She, Fei Qi, Nan Zhang
In this work, the multi-finger gate structure is applied to the short-gate GaN-based HEMT, the influence of the multi-finger gate on the DC and RF characteristics of the GaN-based HEMT are studied theoretically and propose a back barrier and multi-finger gate InAlN/GaN HEMT for high-frequency. In AlGaN/GaN devices, a two-dimensional electron gas (2-DEG) is formed in the HEMT heterojunction due to polarisation.A two-dimensional electron gas (2-DEG) is formed due to polarisation, resulting in lower resistance, higher electron mobility and higher switching speed (Mohanbabu et al., 2021). In this study, the simulation and optimisation of all device characteristics were handled by Silvaco TCAD. The simulation of the structure shows that the radio frequency characteristics of the device can be improved by using multi-finger gate technology.
2-D optimisation current–voltage characteristics in AlGaN/GaN HEMTs with influence of passivation layer
Published in International Journal of Ambient Energy, 2021
Abdelmalek Douara, Abdelaziz Rabehi, Bouaza Djellouli, Abderrezzaq Ziane, Hamza Abid
In recent years, the intense research on AIGaN/GaN HEMT has been widely inspired for high power switching and high-frequency applications, the current focus is to improve the performance metrics of the device (Mimura 2002). The AIGaN/GaN HEMT is a hetero-junction device which takes the advantage of superior electron transport properties and large sheet carrier density produced by built-in polarisation electric field (Sacconi et al. 2001). In AIGaN/GaN heterostructure, the bandgap discontinuity between AIGaN and GaN forms a quantum well-like structure, which accommodates the two -dimensional electron gas (2DEG) and results in increased sheet carrier concentration at the heterojunction interface (Bouguenna et al. 2012). High sheet carrier concentrations of 1013 cm−2 have been obtained in AlGaN/GaN HEMTs, which make them meet the demands of high-power devices (Atlas 2007, Mahon and Skellern 1992).
Controllable electron-momentum filter in a δ-doped magnetically modulated semiconductor nanostructure
Published in Philosophical Magazine Letters, 2019
Sai-Yan Chen, Xue-Li Cao, Meng-Rou Huang, Dong-Hui Liang
The interface in a modulation-doped semiconductor heterostructure contains a high mobility two-dimensional electron gas (2DEG), whose motion can be confined by inhomogeneous magnetic fields on the nanometer scale (for example by depositing nanosized ferromagnetic (FM) stripes on top or bottom of the heterostructue [1]), forming a so-called magnetically confined semiconductor heterostructure (MCSH) [2]. In these kinds of semiconductor nanostructures, the inhomogeneous magnetic field locally influences the motion of electrons. Owing to the low dimensionality, small size, and magnetic confinement, a MCSH possesses many electromagnetic properties [3], such as giant magnetoresistance [4,5], lateral shifts [6], spin filtering [7], etc.