In this paper an integrated wavelength optical filter and photodetector for Visible Light Communication (VLC) is used. The proposed application uses indoor warm light lamps lighting accomplished by ultra-bright light-emitting diodes (LEDs) pulsed at frequencies higher than the ones perceived by the human eye. The system was analyzed at two different wavelengths in the visible spectrum, one in the blue (430 nm) and the other in the red (626 nm) regions, driven at different currents in order to change their optical intensities. The signals were transmitted into free space and measured using a pin-pin photodetector based on a-SiC:H/a-Si:H. This detector behaves as an optical filter with controlled wavelength sensitivity through the use of adequate optical biasing light. The output photocurrent was measured for different optical intensities of the transmitted optical signal and the extent of each signal was tested. An electrical model was used to support the physical operation of the device.

We demonstrate a novel optically tunable photosensitive capacitor (PSC) made from high-purity semi-insulating 4H-SiC. Photosensitive capacitors can provide continuously variable reactive tuning in RF circuitry or enable capacitive-optical sensing applications. Unlike varactors, PSCs often do not require a DC bias voltage to operate. To demonstrate the effect, we fabricated several 1cm x 1cm square photocapacitor devices from bulk material using metal-evaporated Ti/Au contacts using a simple planar parallel-gap geometry. IV curves were taken of the devices using an HP-4145B semiconductor parameter analyzer to verify Schottky behavior as a function of DC bias. The samples were then illuminated with pulsed below-bandgap 470 nm and 590 nm high intensity LED light sources. The resulting data demonstrated an increase in capacitance, Cs, and a drop in resistance, Rs, with increasing optical intensity incident on the device. The observed shifts in both Cs and Rs were repeatable. At a measurement frequency of 33 kHz. Cs increased from its nominal value of 186.7 pF to 575.6 pF while Rs dropped from 150.0 kΩ to 22.4 kΩ. This demonstrates the existence of the photocapacitance effect in high-purity semi-insulating 4H-SiC and thus warrants further investigation. The underlying phenomenon of the effect is suspected to be light interaction with the dominant deep level traps through the Shockley–Read–Hall (SRH) recombination mechanism.

Silicon carbide (SiC) has long been known as a robust semiconductor with superior properties to silicon for electronic applications. Consequently a tremendous amount of international activity has been on-going for over four decades to develop high-power solid state SiC electronics. While this activity has focused on the hexagonal polytypes of SiC, the only form that can be grown directly on Si substrates, 3C-SiC (or cubic SiC), has been researched for non-electronic applications such as MEMS and biosensors. In particular in our group we have pioneered several biomedical devices using 3C-SiC grown on Si substrates, and recently have been investigating the use of this novel material for clean energy applications. This paper first reviews progress made in the area of 3C-SiC electronic devices. Next a review of nearly a decade of biomedical activity is presented, with particular emphasis on the most promising applications: in vivo glucose monitoring, biomedical implants for connecting the human nervous system to advanced prosthetics, and MEMS/NEMS research aimed at allowing for in vivo diagnostic and therapeutic systems for advanced biomedical applications. Recent published work in the area of hydrogen production via electrolysis using 3C-SiC closes the paper as this last application is extremely promising for the burgeoning hydrogen economy and demonstrates a third important application of 3C-SiC on Si – its potential use in clean energy systems.

The performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC a/m-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 μm (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as-grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults (SFs). Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions. Contrast extinction analysis of these dislocation lines reveals they are edge type basal plane dislocations that track the growth direction. Polytype phase transition and stacking faults were observed by high-resolution TEM (HRTEM), in agreement with SWBXT and Raman scattering.

The purpose of this paper is to propose the enhancement of device detectors based on p-n junction in 4H-SiC for nuclear instrumentation. Particular emphasis is placed on the interest on using Boron isotope 10 as a Neutron Converter Layer in order to detect thermal neutrons. Here, we present the main results obtained during several irradiation tests performed in the Belgian Reactor 1 (BR1). We show the capability of our detectors by means of first results of the detector response at different reverse voltage biases and at different reactor power.

Silicon carbide power devices are purported to be capable of operating at very high temperatures. Current commercially available SiC MOSFETs from a number of manufacturers have been evaluated to understand and quantify the aging processes and temperature dependencies that occur when operated up to 350°C. High temperature constant positive bias stress tests demonstrated a two times increase in threshold voltage from the original value for some device types, which was maintained indefinitely but could be corrected with a long negative gate bias. The threshold voltages were found to decrease close to zero and the on-state resistances increased quite linearly to approximately five or six times their room temperature values. Long term thermal aging of the dies appears to demonstrate possible degradation of the ohmic contacts. This appears as a rectifying response in the I-V curves at low drain-source bias. The high temperature capability of the latest generations of these devices has been proven independently; provided that threshold voltage management is implemented, the devices are capable of being operated and are free from the effects of thermal aging for at least 70 hours cumulative at 300°C.

We demonstrate one-dimensional (1D) and two-dimensional (2D) resonant nanoelectromechanical systems (NEMS) derived from nano carbon materials, where the resonance frequency and the quality (Q) factor of the devices are measured experimentally using ultrasensitive optical interferometry. The 1D nano carbon resonators are formed using carbon nanofibers (CNFs) which are synthesized using a plasma-enhanced chemical vapor deposition (PECVD) process, while the 2D nanocarbon resonators are based on CVD grown graphene. The CNFs are prototyped into few-μm-long cantilever-shaped 1D resonators, where the resonance frequency and Qs are extracted from measurements of the undriven thermomechanical noise spectrum. The thermomechanical noise measurements yield resonances in the ∼3–15 MHz range, with Q of ∼200–800. Significant changes in resonance characteristics are observed due to electron beam induced amorphous carbon deposition on the CNFs, which suggests that 1D CNF resonators have strong prospects for ultrasensitive mass detection. We also present NEMS resonators based on 2D graphene nanomembranes, which exhibit robust undriven thermomechanical resonances for the extraction of ultrasmall strain levels.

A novel SiC optical detector that produces optical signal in contrast to the electric signal generated by conventional electrical detectors. The optical detector is a remote sensor providing response to incident photons from a distant object. The incident photons modify the refractive index and, consequently, the reflectance of the doped SiC by altering the electron densities in the valence band and the acceptor energy levels. This variation in the refractive index or reflectance represents the optical signal as the sensor response, which can be determined with a probe laser such as a He-Ne laser or a light-emitting diode. The sensor can be applied to numerous remote sensing applications including high-temperature or harsh environments due to the optical read-out of the detector response with a probe laser. The effects of different dopants on the detector response for sensing different chemical species, or equivalently imaging in different MWIR wavelengths, have been studied and the dopant concentration has been found to affect the optical signal. These results indicate that a new class of SiC detectorsclassified as optical detectors can be produced for a variety of wavelengths using different dopants for numerous applications.