Papers by Keyword: Ballistic Transport

Abstract: Electron transport behaviour in InSb semiconductor significantly changes when the conduction is restricted to two-dimensions. Semiconductor materials are an effective tools to characterize the electron transport in this aspect because the energy separation between transverse modes in a low-dimensional semiconductor device are always inversely proportional to the effective mass, in the same way as for sub-bands in a parabolic potential. Therefore, in this article, a range of novel device geometries were designed, fabricated and characterized to investigate ballistic transport of electrons in low-dimensional InSb structures using surface gated devices to restrict the degrees of freedom (dimensionality) of the active conducting channel. In this framework, designs of gates (i.e., line, loop and solid discussed later) have been used over a range of gate dimensions. Consistent measurement of quantised conductance would be promising for both low power electronics and low temperature transport physics where split gates are typically used for charge sensing. This article presents an experimental results of quantization conductance obtained for the range geometries of novel gates, and some model consideration of the implications of the material choice. Furthermore, the etching techniques (wet and dry) exhibited a significant decrease of ohmic contact resistance from around 35kΩ to only roughly 250Ω at room temperature. Interestingly a possible 0.7 anomaly conduction was observed with a loop gate structure. This work showed perfectly that the two-dimensional electron gases can be formed in narrow gap InSb QWs which makes this configuration device promising candidate for topological quantum computing and next generation integrated circuit applications. Keywords: Quantization conductance, InSb QW, 2DEG, spilt gate structure, ballistic transport.

Abstract: A compact model for the quasi-ballistic cylindrical gate-all-around MOSFET was developed by supplementing the ballistic framework previously disclosed by us with an original energy quantization model. The ballistic mobility is calculated for both degenerate and nondegenerate conditions under collision-free transport. The conventional device electric current showed a remarkable decrease compared with the quasi-ballistic current. The results so obtained have been compared with those obtained from Sentarus device simulator and are found to be in good agreement.

Abstract: With manufacturing technology innovation and progress of electronic devices of semiconductors, dimensions of electronic devices get smaller nowadays. There has been processing of 90nm and 20nm in production. With in-depth research, scientists are more and more interested in molecular devices. Since the size of molecular devices is small, electrons transfer by ballistic transport. In semiconductor devices, when the transport distance is at micrometer or smaller sizes, the ballistic transport phenomena of electrons and holes of carriers occur. This transfer form is not affected by lattice defects, doping, and interaction of crystal interfaces. Since there is no interference of these interactions, carrier’s velocity can be faster several times than common electronic devices, resulting in the doubled operating speed of these devices. Although it is difficult to achieve pure ballistic transport, when the size of semiconductor devices is close to the mean free path of carriers, the speed of carriers will still be greatly improved.

Abstract: Optoelectronic Devices have obtained great interests for many decades. With the development of technology and in-depth research, the devices are scaled down rapidly, reaching sub-millimeter or even nanometer scale, and resulting in various new features. In recent years, a so called Self-Switching Device (SSD) which has diode-like I-V characteristics has attracted more and more attentions. Using Monte Carlo method, we have studied the electron transport in the self-switching device. Simulation results show that when the device size is smaller than the mean free path of electrons, the electron velocity is very different from that of larger device. The electron velocity and the energy become faster and higher, respectively. The reason of this phenomenon is explained by ballistic transport of electrons in the small size device. Since ballistic transport plays an important role in determining the behavior of electrons in small size device, it is need to be included in nanometer scale device modeling.

Abstract: Heteroepitaxial AlGaN/GaN on SiC/Si pseudosubstrate was used to fabricate three-terminal junction devices. Narrow bar and wide bar type active regions were fabricated. The measurement at room temperature showed predicted nonlinear behavior (previously reported about as negative type rectification). Unusual, positive type rectification for two dimensional electron gases was also observed. The electrical characteristics depend on the geometrical configuration of the devices.

Abstract: The singular nature of the Boltzmann transport equation leads to the boundary layer structure around the virtual source in nano-scale device structures. We show that the boundary layer is a key concept to understand the physical mechanism behind quasi-ballistic transport in nano-scale devices. The self-consistent 3D Monte Carlo device simulator is constructed by accurately including the full Coulomb interaction. It is explicitly shown that the Coulomb interaction is indeed a key ingredient for any reliable predictions of device characteristics.

Abstract: . In this paper, in order to determine whether the ballistic current enhancement saturates at very high stress level or can be further improved, the effect of uniaxial stress on the ballistic transport of the double-gated, ultrathin-body p-type silicon nanotransistor is investigated using a self-consistent device simulator, which combines the stress-dependent six-band k.p model and a semiclassical top-of-the-barrier ballistic transport model. Based on a semi-continuum atomistic lattice model, the size-dependent elastic constant correction has been for the first time coupled into this simulator. Our results presented here indicate uniaxial compressive stress at moderate levels improves ballistic performance by about 85% while uniaxial tensile stress slightly reduces ballistic drive current. Interestingly, higher compressively strained channel does not offer higher drive current. Although significant variations in the size-dependent elastic constants are found, the ballistic current shows only a small decrease after considering the elastic constant correction. Furthermore, the competition of injection velocity and carrier density related to hole effective masses is found to play a critical role in determining the performance of the nanotransistors.

Abstract: 3C-SiC is a promising material for high power and high-speed electronic devices as well as in sensors operating at high temperatures or hostile environments. For these reasons, we solved self-consistently the Poisson equation within the quantum Non Equilibrium Green Function Formalism (NEGF) in order to model and compare 3C-SiC and Si nanowire (NW) Field Effect Transistors (FETs) operating in ballistic regime (at room temperature 300 K). As a general conclusion of our calculations, Si and SiC NW FETs have almost the same electrical behavior: they depict the same subthreshold slope and have similar on currents [ION/IOFF (SiC)~81 % ION/IOFF (Si) in case of 4 nm NW cross section side].