Articles you may be interested inA method to determine fault vectors in 4H-SiC from stacking sequences observed on high resolution transmission electron microscopy images

We have observed characteristic temperatures, anneal times, and doping densities that lead to stacking faults and 3C-SiC-like bands in 4H-SiC epilayers. Low energy cathodoluminescence spectroscopy measurements reveal a temperature threshold of 800 °C for emergence of these features in thermally oxidized or argon annealed 4H-SiC with an activation energy ≈2.5 eV. Stacking fault generation and polytype transformation exhibits a strong doping dependence, appearing only in a range of highly doped n-type 4H-SiC. Systematics of these strain and/or electronic effects induced by high N concentrations can be used to control structural instabilities during SiC device fabrication.

Mechanism of ohmic behavior of Al/Ti contacts to p-type 4H-SiC after annealing J. Appl. Phys. 95, 5616 (2004); 10.1063/1.1707215 Schottky barrier height and nitrogen-vacancy-related defects in Ti alloyed Ohmic contacts to n-GaN J. Appl. Phys. 95, 571 (2004); 10.1063/1.1633658Electrical, structural and microstructural characteristics of as-deposited and annealed Pt and Au contacts on chemical-vapor-cleaned GaN thin films We have used low energy electron-excited nanoluminescence ͑LEEN͒ spectroscopy and x-ray photoemission spectroscopy ͑XPS͒ to probe deep level defect states at interfaces of 4H and 6H-SiC with Ti/Pt metallization. These studies aim to identify process conditions under which thermally stable ohmic and Schottky contacts can be obtained on SiC while minimizing the formation of deep level electronic states. Depth-dependent LEEN measurements establish the presence of localized states and their spatial distribution on a nanometer scale. Spectra from the near interface region of 6H-SiC indicate the existence of a SiC polytype with a higher band gap of ϳ3.4 eV. Excitation of the intimate metal-SiC interface reveals a process-dependent discrete state deep within the SiC band gap. XPS measurements reveal consistent differences in the C 1s chemical bonding changes with specific process steps. Analogous chemical treatments of 4H-SiC also produce a lower band gap SiC polytype with ϳ2.5 eV energy extending tens of nanometers beyond the interfaceconfirmed by transmission electron microscopy. This work is the first to show the effect of metalsemiconductor interactions not only on localized states but also on the lattice structure of the semiconductor near the interface.

Approach to optimizing n -Si C Ohmic contacts by replacing the original contacts with a second metalWe have used low energy electron-excited nanoscale luminescence spectroscopy ͑LEEN͒ to study the formation of electronic surface states at metal/ 4H -SiC contacts. These junctions were formed using both low and high reactivity metals to study how the nature of interface chemical bonding affects the interface state formation. We observe evidence for the formation and removal of localized states at energies that have been associated with morphological SiC defects. Metals such as Au and Ag with no strong chemical reactivity exhibited the most pronounced changes. Conversely, chemically-reactive metals such as Ti and Ni exhibited only minor changes and only with high temperature annealing. These observations suggest that native defects rather then metal-specific chemical bonding dominate the interface electronic features.

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