Papers by Keyword: 2DEG

Abstract: To generate both two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) at will in SiC polytype heterojunctions, simultaneous lateral epitaxy (SLE) method has been extended to form epilayers of alternating stacks of 4H-and 3C-SiC, which includes the first formation of single-domain 4H-SiC on 3C-SiC. The process starts with a spontaneous generation of mononuclear 3C-SiC on the atomically flat wide terrace on 4H-SiC, which expands parallel to the basal plane to form a single-domain 3C-SiC layer having the coherent interface with the underlying 4H-SiC layer. Step-controlled epitaxy is then applied using the adjacent 4H-SiC steps to grow an alternative 4H-SiC layer on top of the 3C-SiC surface, forming another coherent interface. The crystal structure, the interface structure, and the carrier distribution of this stacked epilayers was analyzed. Finally, it is demonstrated that 2DEG occurs at the coherent interface between the 3C-SiC Si-and 4H-SiC C-faces and 2DHG at the 3C-SiC C-and 4H-SiC Si-faces.

Abstract: Lateral GaN devices, with a substantial critical breakdown field and increased mobility of two-dimensional electron gas (2DEG), are particularly promising for future power applications. Despite low power consumption by design, further improvements are required in numerous areas, including reliability concerns and switching loss, usually contributing to significant power loss. The research objective concerns the impact of different notch structures on the transfer characteristics of GaN-based high-electron-mobility transistor (HEMT) devices. Thirteen simulated models were produced using COMSOL Multiphysics, incorporating the electrical, structural, and piezoelectric effects of the device. From the results, notch-structure devices demonstrated better electrical characteristics than devices using conventional architecture, particularly a model with a double-notch design. Higher transconductance and maximum drain current were among the improvements, benefiting from the notch structure at the barrier layer.

Abstract: In this work, some properties of the InAs/InGaAs quantum well (QW) were calculated, such as the wave functions and the charge density of the 2D free electron gas (2DEG) by solving the Poisson- Schroedinger equation. The thinner capping layer gives charge densities forming inside the QW that are higher than the thicker values. The optimal thickness of the capping layer can be 10 nm due to the most stable charge density and fully symmetrical wave functions. Our result indicates that higher charge densities can be found with higher Si-delta doping concentrations. However, the distance of the Si-delta doping also affects the charge population. The charge density linearly decreases with a higher Si-delta doping spacer; the thickness was chosen as 7nm. We performed the growth with different concentrations of Si with optimal thicknesses and compared them with the calculated values. There is good agreement between the simulations and experiments with the lower Si-doping concentrations.

Abstract: In this paper, we propose a physics-based analytical model of novel InAlN/GaN High Electron Mobility Transistor (HEMT) by considering the quasi-triangular quantum well with minimal empirical parameters. The derived model is compared for different short and long gate length devices. The results are calibrated and verified with experimental data over a full range for gate and drain applied voltages. Significant improvement in n_s, drain Current, and transconductance are observed for InAlN HEMT making it suitable for nanoscale and microwave analysis in circuit design. Therefore, the proposed model can deal directly with device/physical parameters, and it can be expressed by a very small number of model parameters.

Abstract: AlGaN/InGaN/GaN double heterostructure high electron mobility transistor (HEMT) with In composition from 0.08 to 0.26 were grown by MOCVD. 2DEG density and mobility of different channel In composition were investigated. When In composition below 0.19, 2DEG density increased nearly linearly with In composition, and the mobility decreased a bit. While In composition over 0.19, phase separation became more serious, 2DEG density nearly not changed, and the mobility dropped sharply. A high 2DEG mobility of 1163 cm²/V·s with low sheet resistance of 342Ω/ was obtained with In composition 0.19.

Abstract: Applying theories on quasi-classical particles and the uncertainty relation of quantum mechanics, we deduce the formula of energy uncertainty in energy materials with electric field .We use it to two dimension electron gas (2DEG) in triangular well and get its energy width. Based on these, we find energy width will increase along with the increasing of electronic field intensity. At the same time, the energy width of the first excitated state is wider than the ground state, At the same time, the result of this paper is agreement with the experiment.

Abstract: In this paper, charge control mechanism and carrier features have been precisely investigated in InxGa1-xN/InN/InxGa1-xN based quantum-well double heterostructure high electron mobility transistors (QW-DHEMTs). A study of charge control in the InxGa1-xN/InN/InxGa1-xN structure is performed by self-consistently solving Schrödinger equation in conjunction with Poisson’s equation taking into account the spontaneous and piezoelectric polarization effects. The potential profile and the distribution of electron density in the channel as a function of gate voltage are investigated here. A large conduction band offset of about 2.2eV is obtained for the proposed device for In content x=0.05, which ensure better carrier confinement and higher sheet charge density. The influence of In composition(x) and doping concentration of InxGa1-xN upper barrier on sheet charge density and carrier distributions in channel is also presented. This analysis provides a platform to investigate the InN based QW-DHEMTs and to optimized their design.

Abstract: A common issue in low temperature measurements of enhancement-mode metal-oxide-semiconductor (MOS) field-effect transistors (FETs) in the low electron density regime is the high contact resistance dominating the device impedance. In that case a voltage bias applied across the source and drain contact of a Hall bar MOSFET will mostly fall across the contacts (and not across the channel) and therefore magneto-transport measurements become challenging. However, from a physical point of view, the study of MOSFET nanostructures in the low electron density regime is very interesting (impurity limited mobility [1], carrier interactions [2,3] and spin-dependent transport [4]) and it is therefore important to come up with solutions [5,6] that work around the problem of a high contact resistance in such devices (c.f. Fig. 1 (a)).

Abstract: In this work the electrical and structural properties of AlGaN/GaN heterostructures grown onto 8°-off-axis 4H-SiC epilayers were investigated. A morphological and structural analysis of the samples showed the presence of “V-shaped” near-surface defects in the AlGaN layer, with a preferential orientation along the miscut direction [11-20]. In the presence of these defects an anisotropy of the current-voltage characteristics of high electron mobility transistors (HEMTs), fabricated with two different orientations, was observed. The sheet carrier density ns and the channel mobility n were determined from the device characteristics. The results were discussed considering the possible implications for AlGaN/GaN HEMT technology.

Abstract: In this paper, there is an attempt to present the two dimensional electron gas (2DEG) transport characteristics of AlxGa1-xN/(AlN)/GaN-based High Electron Mobility Transistor (HEMT) using a self-consistent numerical method for calculating the conduction-band profile and subband structure. The subband calculations take into account the piezoelectric and spontaneous polarization effects and the Hartree and exchange-correlation interaction. Here the dependency of conduction band profile, subband energies, 2DEG sheet concentration and sheet resistance on various Al mole fractions of AlxGa1-xN barrier layer are presented by incorporating simulation as well as available experimental data. Introduction of very thin binary AlN layer at the heterojunction of AlxGa1-xN/GaN resulting high mobility at high sheet charge densities by increasing the effective and decreasing alloy disorder scattering. Devices based on this structure exhibit good DC and RF performance as an increase of . Owing to high 2DEG density , the proposed device leads to operate in microwave and millimeter wave applications.