Novel SiC detector based on optical signal instead of electrical signal
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Novel SiC detector based on optical signal instead of electrical signal Geunsik Lim,1 Tariq Manzur,2 and Aravinda Kar1 1CREOL, The College of Optics and Photonics, Laser-Advanced Materials Processing Laboratory, Departments of MAE and MSE, University of Central Florida, Orlando, Florida 32816-2700, U.S.A. 2S&T Lead, I&EW, Undersea Warfare Electromagnetic Systems Development, Building 1319, 1176 Howell Street, Newport, RI 02841-1708, U.S.A. ABSTRACT 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 readout 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. INTRODUCTION Crystalline silicon carbide (SiC) is chemically inert and it has high electric breakdown strength, thermal conductivity and mechanical strength, which make it an excellent material for numerous high-temperature applications including high-voltage and high-current devices, and sensors for harsh environments. Different SiC device architectures such as capacitors, transistors and Schottky diodes have been studied as potential gas sensors. Andersson et al. [1] developed a new generation SiC field effect transistor (FET) for gas sensing applications, and Darmastuti et al. [2] and Bur et al. [3] employed the SiC FET for detection of methanol leakage and quantification of NO x , respectively. Zhang et al. [4] studied boron-doped carbon nanotubes for sensing HCN, and Wu et al. [5] examined SiC nanotubes as gas sensors for CO and HCN. The conventional chemical sensors generally measure the changes in electrical properties, such as resistance or capacitance, of a thin film that is in contact with the chemical of interest. Optical gas sensors, on the other hand, rely on the modifications in optical properties, such as refractive index, by the characteristic radiation emitted by the chemical of interest. Optical gas sensors can operate remotely with significant stand-off from the source of the chemical, possess rapid response time for dynamic envir
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