A correlation between bulk leakage current density and threading dislocation density in silicon–germanium mesa-isolated diodes fabricated on relaxed graded buffer layers is presented. Si0.75Ge0.25 p-i-n diodes were grown on SiGe graded buffers with different grading rates. Graded buffers with different grading rates yielded “virtual substrates” with varying densities of threading dislocations. Bulk leakage current densities were differentiated from surface leakage currents by using p-i-n diodes with different areas. We demonstrate that the increase in bulk leakage current density in SiGe p-i-n diodes can be modeled by generation processes assisted by deep levels related to threading dislocations.

No abstract

No abstract

Under typical growth conditions, strain levels greater than or equal to 10−4 are shown to influence thin film surface morphology and strain relaxation pathways. Misfit and threading dislocations in relaxed heterostructures produce long wavelength undulations on the surface and shallow depressions, respectively. Threading dislocation densities greater than ∼105–106 cm−2 in relaxed heterostructures must be due to increased impediments to dislocation motion, which in turn originate from the effect of the misfit dislocations on the surface morphology. Under typical growth conditions, the origin of strain-induced surface features can be identified by recognizing the length scale at which the features occur.

We demonstrate that carbon molecular weight growth chemistry can continue to occur when polycyclic aromatic hydrocarbons (PAH), produced by localized fuel rich pockels within an incinerator, disperse into the near-stoichiometric bulk flow characteristic of the unit. Naphthalene, a model PAH, was added to a near-stoichiometric (¢ = 1.2) post-flame combustion flow produced by premixed C,H./O,/N,/Air combustion in a jet-stirred/plug-flow reactor system (JSR/PFR), and the results compared against those from a fuel rich (¢ = 2.2) post-flame combustion flow without naphthalene addition. In both experiments, the PFR was sampled for soot (CH,C1, insolubles), tar (CH,CI, solubles; PAH), C,H, and other light gases.The results indicate that naphthalene addition to the ¢ = 1.2 flow produces PAH in the naphthalene (MW = 128)to cyclopenta[cd]pyrene(MW = 226) fraction at exactly the same total mass concentration as observed in the ¢ = 2.2 flow without naphthalene addition. Similarly, the rate of growth of soot mass is approximately the same in both cases. In contrast, the concentration of high molecular weight PAH (PAH > MW 226) produced is 3 times less, and that ofC,H, is 100 to 600 times less in the ¢ = 1.2flow with C,oH, addition than in the ¢ = 2.2 flow without CIOH, addition. These data suggest that under our reactor conditions, PAH in the 128 to 226 amu molecular weight range are more important contributors to the soot growth process than either C,H, or high molecular weight PAH.