Large Area Silicon Carbide Research Articles

Characterization of newly developed large area SiC sensors for the NUMEN experiment

First prototypes of large area, p–n junction, silicon carbide (SiC) detectors have been produced as part of an ongoing programme to develop a new particle identification wall for the focal plane detector of the MAGNEX magnetic spectrometer, in preparation for future NUMEN experimental campaigns. First characterizations of sensors from two wafers obtained with epitaxial silicon carbide growth and with different doping concentration are presented. Current (I–V) and capacitance (C–V) characteristics are investigated in order to determine the full depletion voltage and the doping profile. Radioactive α-sources are used to measure the energy resolution and estimate the depletion depth.

SO2 Monitoring With Solid State-Based UV Spectroscopy Compact Apparatus

We propose a solid state-based spectroscopy compact apparatus for monitoring environmental SO2, particularly suitable, for example, for volcanic applications. A prototype system, with a 170-mm long optical path, was assembled and tested using a commercial LED operating at 285 nm and a large area silicon carbide. The laboratory tests were carried out using calibrated quartz cuvettes containing SO2 at fixed concentrations and standard SO2 gas with 20% of O2 and complemented with N2 dry gas to fill the optical system chamber. Optical signal attenuations in the chemically interactive chamber follow the Beer-Lambert-Bouguer law in all the performed tests and a 0.16 ppm/pA nominal chemical resolution and ± 0.8 ppm concentration error were obtained from the experimental data for the current prototype.

Large Area Silicon Carbide Photodiode, and Monolithic Readout Design and Fabrication

We are in the process of designing and fabricating a very large area (> 4mm2) and extremely low dark current silicon carbide ultraviolet photodiode with a readout circuitry monolithically fabricated on the same die. This is a large area silicon carbide based active pixel sensor (APS), capable of measuring low power density deep ultraviolet photons as well as low energy particles. To this end, we have already fabricated several large area photodiodes with low dark current values and large ultraviolet responsivities. We here report the electrical and optical measured performance of various size photodiodes we have fabricated.

Large-area SiC membrane produced by plasma enhanced chemical vapor deposition at relatively high temperature

Advances in the growth of silicon carbide (SiC) thin films with outstanding thermal and mechanical properties have received considerable attention. However, the fabrication of large-area free-standing SiC membrane still remains a challenge. Here, the authors report a plasma enhanced chemical vapor deposition process at a relatively high temperature to improve the free-standing SiC membrane area. A systematic study on the microstructural, mechanical, and optical properties of hydrogenated polycrystalline silicon carbide (poly-SiCx:H) thin films deposited at 600 °C with different annealing temperatures has been performed. In the as-deposited state, SiCx:H thin films show a polycrystalline structure. The crystallinity degree can be further improved with the increase of the postdeposition annealing temperature. The resulting process produced free-standing 2-μm-thick SiC membranes up to 70 mm in diameter with root mean square roughness of 3.384 nm and optical transparency of about 70% at 632.8 nm wavelength. The large-area SiC membranes made out of poly-SiCx:H thin films deposited at a relatively high temperature can be beneficial for a wide variety of applications, such as x-ray diffractive optical elements, optical and mechanical filtering, lithography mask, lightweight space telescopes, etc.

Characterization of a Large Area Silicon Carbide PiN Diode at Temperatures up to 900°C

For the first time, a large area Silicon Carbide (SiC) PiN diode was measured to determine the forward and reverse characteristics at temperatures up to 900°C. The diode characterized had a chip area of 64 mm2 and used a conventional SiC PiN structure with a 75 um N type blocking layer thickness. A normal rating for this device at room temperature would be 50 amps at 100 A/cm2 and 6 kV. Since a package capable of operating at 900°C was not available, methods were developed to heat and verify the temperature of the diode die, provide electrical connections to the die and provide adequate insulation to minimize temperature gradients across the die. Even at this extreme temperature the diode maintained typical diode characteristics and maintained surprisingly good performance.

Mapping of Defects in Large-Area Silicon Carbide Wafers via Photoluminescence and its Correlation with Synchrotron White Beam X-Ray Topography

Comparative studies of defect microstructure in 4H-SiC wafers have been carried out using photoluminescence (PL) imaging and grazing-incidence Synchrotron White Beam X-ray Topography. Images of low angle grain boundaries on the PL images correlate well with SWBXT observations, and similar correlation can be established for some micropipe images although the latter is complicated by the overall level of distortion and misorientation associated with the low angle grain boundaries and the fact that many of the micropipes are located in or close to the boundaries. This validation indicates that PL imaging may provide a rapid way of imaging such defect structures in large-scale SiC wafers.

Large area silicon carbide devices fabricated on SiC wafers with reduced micropipe density

Silicon carbide devices are being developed for high-power applications. High current operation of these devices is limited by substrate quality. In SiC substrates, micropipes (sometime referred to as micro pores) are a common defect. The presence of even a single micropipe defect intersecting the active region of the device has been shown to produce pre-mature electric breakdown. As a result, the active area of SiC devices usually does not exceed 1 mm 2. In order to fabricate high-power SiC devices, operating at currents of 100 A and higher, the device area must exceed 10 mm 2 (using reasonable values of current density possible in SiC). Recently, we reported on the fabrication of silicon carbide epitaxial wafers with reduced micropipe density (Rendakova et al., J. Electron Mater. 27 (1998) 292). The best R&D wafers 35 mm and 41 mm in diameter, both 6H and 4H polytypes, have no micropipes. We proposed these wafers as substrates for SiC high-power devices (Chelnokov et al., Diamond and Related Mater. 6 (1997) 1480–1484). In this paper, we report on the fabrication of large area Schottky barriers (up to 8 mm 2) based on 4H-SiC layers grown on SiC wafers with reduced micropipe density. Schottky barriers produced on this material demonstrate that large devices can be fabricated without the usual degradation associated with the presence of micropipes.