Aveek Chatterjee

First-principles-based investigation of kinetic mechanism of SiC(0001) dry oxidation including defect generation and passivation

The key stages of the dry oxidation of the SiC(0001) surface are analyzed based on first-principles calculations. It is found that an abrupt SiC/SiO2 interface model results in a large activation barrier of oxygen penetration to the silicon carbide, and thus the penetration is probably the rate-limiting step for the entire dry-oxidation process. The subsequent reactions of SiC oxidation after oxygen penetration are investigated, and it is found that CO release is competing with carbon dimer formation. These dimers probably are responsible for near-interface traps in the silica layer generated during SiC oxidation. The possible passivation reactions of a carbon dimer defect by active species, such as O2, NO, and H2 are investigated. It is found that an oxygen molecule can break a Si–C bond via dissociation in the triplet state and finally can produce two CO molecules from the carbon dimer defect. The NO molecule can easily break a Si–C bond of a carbon dimer defect and form cyano groups –CN, which can fina...

Multiscale Modeling and Analysis of the Nitridation Effect of SiC/SiO2 Interface

We explain the role of nitrogen in simultaneously increasing the inversion channel mobility and reducing the threshold voltage of SiC MOSFET. A variety of computational techniques have been used to compute the atomic scale configuration of a nitridated SiC/SiO2 interface, and the corresponding change in Fermi level, inversion channel mobility, and threshold voltage. X-ray photoelectron spectroscopy (XPS) has been used to investigate the SiC/SiO2 interface to determine the nitrogen concentrations and chemical bonding. We elucidate the physics behind improved channel mobility due to NO anneal and demonstrate that the trade-off between threshold voltage and inversion channel mobility can be correlated to the extent of nitridation.

Linear Fresnel Reflector based Solar Radiation Concentrator for Combined Heating and Power

We have designed and realized a test rig to characterize concentrated solar‐based CHP (combined heat and power) generator. Cost benefit analysis has been used to compare alternate technologies, which can cogenerate electrical and thermal power. We have summarized the experimental setup and methods to characterize a concentrated solar thermal (CST) unit. In this paper, we demonstrate the performance data of a concentrated solar thermal system.

Atomistic Scale Modeling and Analysis of Sodium Enhanced Oxidation of Silicon Carbide

We explain the phenomenon of sodium enhanced oxidation (SEO) using computational techniques, and analyze a set of probable hypotheses, which can elucidate the observation of high inversion channel mobility achieved with SEO. The ability of the Na to screen the interface traps, reduce carbon cluster type of defect formation, and enhance the oxidation rate can be explained using these calculations. We observe an increased availability of electrons near the interface in the presence of Na. The sodium atom also helps in breaking the intramolecular oxygen bond. The electronic and atomic structure of the interface cluster, and electric field computations showed that the carbon cluster formed at the oxide side of the interface could be screened by the Na ion.

Silicon carbide oxidation in the presence of cesium: Modeling and analysis

In this work we have focused on investigating the interaction of cesium (Cs) atom/ion with the oxidant and carbon cluster defects at the SiC/SiO2 interface using atomistic scale computational techniques and experimental characterization methods. We observe that Cs behaves significantly different from sodium (Na) at the SiC/SiO2 interface. Our analyses indicate that Cs tends to form a strong bond with the incoming oxygen molecule, leading to the formation of Cs oxide and suboxides. Results suggest that Cs does not reduce the penetration barrier of the impinging oxidant (O2 molecule). Also, unlike Na, Cs is unable to increase the Fermi energy of SiC/SiO2 interface. Finally, lateral metal–oxide–semiconductor field-effect transistors (MOSFETs) were fabricated (using Cs) yielding mobilities less than 1 cm2/V s versus ∼100 cm2/V s fabricated using Na.

Evaluation of 4H-SiC Carbon Face Gate Oxide Reliability

The gate oxide reliability and channel mobility of carbon face (000-1) 4H Silicon Carbide (SiC) MOSFETs are investigated. Several gate oxidation processes including dry oxygen, pyrogenic steam, and nitrided oxides were investigated utilizing MOS capacitors for time dependent dielectric breakdown (TDDB), dielectric field strength, and MOSFETs for inversion layer mobility measurements. The results show the C-face can achieve reliability similar to the Si-face, however this is highly dependent on the gate oxide process. The reliability is inversely related to the field effect mobility where other research groups report that pyrogenic steam yields the highest electron mobility while this work shows it has weakest oxide in terms of dielectric strength and shortest time to failure.

Atomistic Scale Modeling of Factors Affecting the Channel Mobility in 4H-SiC MOSFETs

We have identified the crystal planes of 4H-SiC, interfacing with gate oxide, which will lead to minimum defect density and lowest interface corrugations. The atomic surface density, surface energy, and surface roughness of various crystal planes of 4H-SiC have been computationally characterized using Molecular Dynamics simulations. We have also investigated the screening distances of defects in SiO2 and SiC using a multiscale approach.