MWIR room temperature photodetector based on laser-doped silicon carbide

Abstract

MWIR photon detector in the mid-infrared wavelength (2-5 μm) range is developed using crystalline silicon carbide substrates. SiC, which is a wideband gap semiconductor, is laser-doped to create a dopant energy level corresponding to a quantum of energy for the required operating wavelength of the detector. The photons of the objects in the field of view excite the electrons of the detector, leading to changes in the refractive index. This change in the optical property of the detector can be measured remotely with a laser beam, such as a He-Ne laser beam of wavelength 632.8 nm, which makes it a wireless detector. While many IR detectors require cryogenic cooling (77 K) to suppress thermal generationrecombination processes in order to operate with good detectivity, the SiC-based detector can operate at room temperature with excellent performance. An n-type 4H-SiC substrate has been doped with Ga by a laser doping technique to create a detector element for the MWIR wavelength of 4.21 μm corresponding to the photon energy 0.30 eV. The dopant energy level is confirmed by optical absorption measurements. The change in the refractive index is studied as a function of absorbed irradiance on the detector. The experimental result shows that the Ga-doped 4H-SiC sample can be used for MWIR detectors.