Both 3C-SiC and 6H-SiC single-crystal films can be grown on vicinal (0001) 6H-SiC wafers. We have found that oxidation can be a powerful diagnostic process for (1) ‘‘color mapping’’ the 3C and 6H regions of these films, (2) decorating stacking faults in the films, (3) enhancing the decoration of double positioning boundaries, and (4) decorating polishing damage. Contrary to previously published oxidation results, proper oxidation conditions can yield interference colors that provide a definitive map of the polytype distribution for both the Si face and C face of SiC films. Defects were more effectively decorated by oxidation on the Si face than on the C face.

We have found that, with proper pregrowth surface treatment, 6H-SiC single-crystal films can be grown by chemical vapor deposition (CVD) at 1450 °C on vicinal (0001) 6H-SiC with tilt angles as small as 0.1°. Previously, tilt angles of greater than 1.5° were required to achieve 6H on 6H at this growth temperature. In addition, 3C-SiC could be induced to grow within selected regions on the 6H substrate. The 3C regions contained few (or zero) double-positioning boundaries and a low density of stacking faults. A new growth model is proposed to explain the control of SiC polytype in this epitaxial film growth process.

Schottky diodes composed of palladium deposited on silicon carbide (Pd/SiC) detect hydrogen and hydrocarbon gases at elevated temperatures with high sensitivity. Previous examination of the properties of the Pd/SiC structure indicated that its forward current responded to the presence of hydrogen even after extended annealing at 425 °C. However, drift in the sensor properties suggested that stabilization of the diode structure was necessary. In this work, we examine the effects of placing a thin layer of silicon dioxide (SiO2) between the Pd and the SiC. Both Pd/SiC and Pd/SiO2/SiC diodes are annealed at 425 °C for 140 h and the electronic and interfacial properties of the annealed diodes are compared. The electronic properties and sensitivity to hydrogen of both diodes change significantly due to the annealing. Scanning electron microscopy and Auger electron spectroscopy indicate that the surface and interfacial properties of the diodes are very different. The Pd/SiC diode has a broad interface region with palladium silicides (PdxSi) distributed throughout the Pd. In contrast, the Pd/SiO2/SiC diode has a sharp interface with significantly less PdxSi formation. A silicon oxide (SiOx) layer has formed in the near surface region of the Pd which likely accounts for the relative insensitivity of the Pd/SiO2/SiC diode to hydrogen. The experimental data suggest that the mechanism for this SiOx formation is likely two-dimensional diffusion between the Pd and the surrounding SiC surface. While the thin SiO2 layer results in a sharp interface between the Pd and SiC, further stabilization of the diode structure is necessary for long term, high temperature sensor operation.

Dry-oxidized n-type 6H-SiC metal-oxide-semiconductor capacitors are investigated using quasistatic capacitance versus voltage (C-V), high-frequency C-V, and pulsed high-frequency capacitance transient (C-r) analysis over the temperature range from 297 to 573 K. The quasistatic C-V characteristics presented are the first reported for 6H-SiC MOS capacitors, and exhibit startling nonidealities due to nonequilibrium conditions that arise from the fact that the recombination/ generation process in 6H-SiC is extraordinarily slow even at the highest measurement temperature employed. The high-frequency dark C-V characteristics all showed deep depletion with no observable hysteresis. The recovery of the high-frequency capacitance from deep depletion to inversion was used to characterize the minority-carrier generation process as a function of temperature. Zerbst analysis conducted on the resulting C-r transients, which were longer than 1000 s at 573 K, showed a generation lifetime thermal activation energy of 0.49 eV

Current-voltage characteristics of Au contacts formed on ~-SiC films grown heteroepitaxially on both nominally (100) oriented and off-axis (100) silicon substrates have been investigated. These contact diodes are rectifying, and very low reverse leakage currents are observed, particularly in off-axis silicon substrates. The diode ideality factor is between 1.3 and 2.0 in all cases except in nominal (100) silicon substrates where it is greater than two. Logarithmic plots of the I-V characteristics in the forward direction indicate space charge limited current conduction through the active volume of the diodes. The ~-SiC films grown on nominally (100) oriented substrates show the presence of two deep levels located approximately between 0.26 and 0.38 eV below the conduction bandedge. In some films on nominal (100) substrates, the I-V characteristics are also influenced by additional traps which are exponentially distributed in energy with a maximum occurring at the conduction bandedge. In contrast, the films deposited on off-axis substrates have only one deep level located at approximately 0.49 eV for the 2 ~ off(100) substrates and 0.57 eV for the 4 ~ off(100) substrates. Previous microstructural analysis revealed that the nature and density of defects in the p-SiC heteroepitaxial films on both nominal and off-axis (100) silicon are similar except that the films on nominal (100) substrates have a high density of antiphase domain boundaries. Therefore, the presence of the shallower deep-level states observed in the p-SiC films grown on nominal (100) substrates is speculated to be due to the electrical activity of antiphase domain boundaries.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.126.162.126 Downloaded on 2015-03-09 to IP