Papers by Keyword: 6H-SiC

Abstract: 6H-SiC and 3C-SiC structural, electronic and optical properties have been calculated by applying the principles of density functional theory based on the plane wave pseudo-potential. This method is implanted in Wien2k Software. Structural parameters are calculated at the level of Perdew Burke and Ernzerhof (PBE) parameterized generalized gradient approximation (GGA). The obtained results given in Table I were compared to the experimental data in relation with the lattice constant hexagonal ration c/a and the band gap value parameters of 6H-SiC and 3C-SiC, there was a very accurate concordance. The superior gap value and the good absorption coefficient drives us to realize a p⁺nn⁺ solar cell device using SILVACO Software. The 3C-SiC material resulted in a considerable performance for photovoltaic applications.

Abstract: Comparison of C-V characteristics and interface trap distribution for 6H-SiC MOS capacitor with AlN and HfO₂ as high-k dielectric are presented. It is observed that the transition from accumulation to inversion requires a small change in gate voltage for HfO₂ compared to AlN. Furthermore, larger shift in flat band voltage with respect to frequency is observed in case of AlN. A larger change in capacitance with respect to voltage and flat band voltage shift with respect to frequency for AlN indicated a poor choice for MOS capacitor compared to HfO₂.

Abstract: In recent years, graphene has sparked the interest of researchers due to its promising electrical and physical attributes. These attributes make it highly suitable to develop electronic devices with ultra-high mobility of charge carriers. Meanwhile silicon carbide (SiC), a wide bandgap semiconductor material, is being used for high temperature optoelectronic applications. SiC has more than 250 different crystalline forms, these are called polytypes. Some of these polytypes (such as 4H-SiC, 6H-SiC and 3C-SiC) have exceptional physical and electrical properties. Electronic devices which have SiC and graphene as their constituent materials may combine the outstanding attributes of both materials. This article attempts to simulate electronic devices having SiC and graphene as their constituent materials. For this purpose, simulations of a novel nn-heterojunction 4H-6H/SiC diodes with the inclusion of an armchair nanoribbon layer have been carried out. All of the simulations have been run using QuantumWise Atomistix Toolkit (ATK) software, which is an atomic scale electronic device simulator. The density of the states, charge carrier densities and current-voltage curves of the simulated devices have been computed. The simulation results showed a significant improvement in the electrical conduction properties of nn-heterojunction 4H-6H/SiC diodes after the inclusion of the armchair graphene nanoribbons. These simulations provide the groundwork for our future experiments, which will be targeted on fabricating high mobility diodes and/or field effect transistors.

Abstract: In the last decade, silicon carbide (SiC) has gained a remarkable position among wide bandgap semiconductors due to its high temperature, high frequency, and high power electronics applications. SiC heterostructures, based on the most prominent polytypes like 3C-SiC, 4H-SiC and 6H-SiC, exhibit distinctive electrical and physical properties that make them promising candidates for high performance optoelectronic applications. The results of simulations of nn-junction 3C-4H/SiC and 6H-4H/SiC heterostructures, at the nanoscale and microscale, are presented in this paper. Nanoscale devices are simulated with QuantumWise Atomistix Toolkit (ATK) software, and microscale devices are simulated with Silvaco TCAD software. Current-voltage (IV) characteristics of nanoscale and microscale simulated devices are compared and discussed. The effects of non-ideal bonding at the heterojunction interface due to lattice misplacements (axial displacement of bonded wafers) are studied using the ATK simulator. These simulations lay the groundwork for the experiments, which are targeted to produce either a photovoltaic device or a light-emitting diode (working in the ultraviolet or terahertz spectra), by direct bonding of SiC polytypes.

Abstract: The optical response of graphene on 6H-SiC was investigated by means of IR-reflectance measurements. Thereby, the anisotropy of the substrate is considered and its influence was studied by performing measurements with s- and p-polarized light. The anisotropy causes a splitting of the reststrahlen band in p-polarization, but does not affect spectra recorded with s-polarization. In both cases a thin film approximation was used to simulate the reflectance spectra. A model consisting of SiC, graphene and air enables the extraction of the graphene layer count.

Abstract: Three-inch 6H-SiC bulk crystals were grown by the PVT method on the seeds processed by different treatments. The influences of seed surface morphology and subsurface damage on the dislocation density were investigated. The seed surface morphology was characterized by atomic force microscopy (AFM). The extent of the subsurface damage was estimated by electron back-scattered diffraction (EBSD) and Band Contrast (BC) value. The distribution and density of the dislocations were observed by optical microscopy (OM). The results showed that the pit density performed by H₂ 1400°C etching was nearly one order of magnitude lower than that by mechanical polishing (MP) process. So H₂ etching processed at 1400°C for 2h could completely remove the subsurface damage, compared with the MP process with the deep surface damage.

Abstract: The mean projected ranges and range straggling for energetic 200 – 500 keV Yb ions implanted in 6H-SiC were measured by means of Rutherford backscattering followed by spectrum analysis. The measured values are compared with Monte Carlo code (SRIM2012) calculations. It has been found that the measured values of the mean projected range are good agreement with the SRIM calculated values; for the range straggling , the difference between the experiment data and the calculated results is much higher than that of .

Abstract: Over the last decade, a relatively in-depth research on the different structures and types of the full SiC pressure sensors including the piezoresistive, the capacitive and the optical SiC pressure sensors etc. has been conducted with a view to realizing the pressure measurement in high temperature circumstances. The piezoresistive SiC pressure sensor has gradually become the focus of research due to its simple structure and convenience application. In our research, the piezoresistance strip is designed on the deep-etching sensitive circular diaphragm formed via deep etching. Firstly, the 6H-SiC strain coefficient GF value is compared on the radial direction and the transverse direction by analyzing the circular diaphragm deformation theory. It’s concluded that both in the radial direction, four resistance strips are assigned in the center of circular diaphragm and along the edge respectively, with equal number on these two locations. Better consistency and sensitivity are achieved by this solution. Secondly, the design size of the sensitive circular diaphragm and the pressure resistance strips are determined with the expected work temperature and the target measuring range being taken into consideration. The final layout scheme design of four pressure resistance strips is determined through simulation on the consideration of the thermal stress caused by the AlN packaging.

Abstract: Magnetic properties of 6H-SiC doped with transition metal (TM) atoms are calculated using the density functional theory method (DFT). It is shown that TM doped in a 6H-SiC host may have both magnetic and nonmagnetic states. From the figures of their density of states (DOS) and partial density of states (PDOS) and to compare the energy differences between ferromagnetic and nonmagnetic states, we demonstrate that Cr and Mn-doped 6H-SiC emerge a half-metallic ferromagnetic state, Co and Ni-doped 6H-SiC create very little magnetic features, while Fe-doped 6H-SiC is in the nonmagnetic state. We also calculate the energy differences between ferromagnetic and antiferromagnetic of Cr, Mn and Fe-doped 6H-SiC in the doping concentration (8.34%). It is found that the energy of the antiferromagnetic state is lower than that of the ferromagnetic state.

Abstract: In order to remove the cutting marks on the cutting surface of 6H-SiC single crystal wafer, experiments were conducted to investigate the effect of the abrasive characteristics (types, grain size, concentration and mixed abrasives) on the lapping performance of 6H-SiC single crystal wafer, then the removal mechanism of the abrasive grains in the lapping process was studied. Results indicate that the abrasives with larger grain size and higher hardness can result in a higher material removal rate while the abrasives with smaller grain size and lower hardness can achieve a lower surface roughness value. When the concentration of the abrasives is 7.69 wt%, a good lapping effect was obtained. Lower surface roughness value Ra can be obtained with a high material removal rate by using certain proportion mixed abrasives. Selecting appropriate abrasives can obtain a high surface quality of 6H-SiC wafer with a high efficiency.