19 October 2012 Uncooled MWIR SiC optical detector response dynamics and digital imaging
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Abstract
Crystalline silicon carbide (SiC) is a wide bandgap covalent semiconductor material with excellent thermo-mechanical and optical properties. While the covalent bonding between the Si and C atoms allows n-type or p-type doping by incorporating dopant atoms into both the Si and C sites, the wide bandgap enables fabrication of optical detectors over a wide range of wavelengths. To fabricate a mid-wave infrared (MWIR) detector, an n-type 4H-SiC substrate is doped with Ga using a laser doping technique. The Ga atoms produce an acceptor level of 0.30 eV which corresponds to the MWIR wavelength of 4.21 μm. Photons of this wavelength excite electrons from the valence band to the acceptor level, thereby modifying the electron density, refractive index, and reflectance of the substrate. This change in reflectance constitutes the detector response. The dynamics of the detector response are studied by placing a chopper at a constant angular velocity between the MWIR radiation source and the detector. The imaging capability of the detector is established by reflecting incoherent light at a wavelength of 633 nm, which is produced by projecting illumination from a light-emitting diode (LED) off the detector towards a CMOS camera and examining the digital output of the camera to determine the relative intensity of the incident radiation. In addition, a mathematical model is presented to analyze the dynamic response and determine the electron density and lifetime in the acceptor level.
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John Zeller, Tariq Manzur, Aravinda Kar, "Uncooled MWIR SiC optical detector response dynamics and digital imaging", Proc. SPIE 8540, Unmanned/Unattended Sensors and Sensor Networks IX, 854007 (19 October 2012); doi: 10.1117/12.2009521; https://doi.org/10.1117/12.2009521
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