Uncooled $\text{SI}_{\mathrm{x}}\text{GE}_{\mathrm{y}}\mathrm{O}_{1-\mathrm{x}-\mathrm{y}}$ Microbolometer Stack for LWIR Detection

Abstract

This paper presents design, fabrication, characterization, and noise reduction of two uncooled Si 0 . 622 Ge 0.298 O 0.08 microbolometer stacked in a single pixel. Each microbolometer captures a portion of the spectrum across the long wavelength infrared region (LWIR) and the combined structure was optimized to maximize the total absorptance, transmittance, and reflectance of the individual surfaces with Frequency Selective Surface (FSS). The inclusion of the FSS on the bottom microbolometer permits engineering the IR absorptance with respect to wavelength. While the top microbolometer utilizes the need for a ¼-wave resonant cavity under the microbolometer. In addition, the metasurface can significantly improve the electrical performance of the temperature-sensing layer. These parameters scale with the periodicity and area fraction of the metasurface. The voltage noise power spectral density was reduced by annealing the devices in vacuum. The measured responsivity and detectivity approached 104 V/W and 108 cm Hz1/2/W for the bottom microbolometer with FSS.