Cross-Sectional Carrier Lifetime Profiling and Deep Level Monitoring in Silicon Carbide Films Exhibiting Variable Carbon Vacancy Concentrations

The carrier lifetime control over 150 μm thick 4H-SiC epitaxial layers via thermal generation and annihilation of carbon vacancy (VC) related Z1/2 lifetime killer sites is reported. The defect developments upon typical SiC processing steps, such as high- and moderate-temperature anneals in the presence of a carbon cap, are monitored by combining electrical characterization techniques capable of VC depth-profiling, capacitance–voltage (CV) and deep-level transient spectroscopy (DLTS), with a novel all-optical approach of cross-sectional carrier lifetime profiling across 4H-SiC epilayer/substrate based on imaging time-resolved photoluminescence (TRPL) spectroscopy in orthogonal pump-probe geometry, which readily exposes in-depth efficacy of defect reduction and surface recombination effects. The lifetime control is realized by initial high-temperature treatment (1800 °C) to increase VC concentration to ≈1013 cm−3 level followed by a moderate-temperature (1500 °C) post-annealing of variable duration under C-rich thermodynamic equilibrium conditions. The post-annealing carried out for 5 h in effect eliminates VC throughout the entire ultra-thick epilayer. The reduction of VC-related Z1/2 sites is proven by a significant lifetime increase from 0.8 to 2.5 μs. The upper limit of lifetimes in terms of carrier surface leakage and the presence of other nonradiative recombination centers besides Z1/2, possibly related to residual impurities such as boron are discussed.publishedVersio

Lithiation of Carbon terminated silicon Carbide Surface

Master's thesis in Mathematics and physicsWith the aim of searching for a promising Anode material for lithium ion batteries, quantum espresso modelling of the introduction of Lithium into the carbon terminated Silicon Carbide (SiC) Surface layers with the bottom layers treated with hydrogen to prevent dangling bond. We employ first principle (Ab-initio) Density functional theory (DFT) calculations with inclusion of gradient correction and periodic boundary conditions to obtain the convergent energies of the different doped structures at the Surface and Near surface layers of the super cell and also to understand the structural, electronic and lithium absorption properties on the surface. we can show that the absorption of Lithium by silicon Carbide is energetically more stable at the surface than the bulk. Energy differences will turn to decrease as we increase the concentration of Lithium into the vacancies