Modeling and characterization of high TCR, low noise Si/Si1-xGex multi-quantum well detector for uncooled microbolometers
Shafique, Atia (2018) Modeling and characterization of high TCR, low noise Si/Si1-xGex multi-quantum well detector for uncooled microbolometers. [Thesis]
Uncooled infrared focal plane arrays (IR FPAs) have seen unprecedented growth over the last decade and ubiquitously extending its application beyond the military realm into various diverse areas such as: surveillance, security and law enforcement, thermography (predictive maintenance, building inspection), industrial process control, automotive safety and medical imaging. The uncooled microbolometers are mainly used for imaging in long wave infrared spectral range (LWIR). In the recent years, the e orts made for the technical evolution of the microbolometer involves: pixel size reduction, new materials and designs to enhance the detection and integration capability. Currently, Vanadium oxide VOx together with a-Si based FPAs have the major share in the uncooled imaging market. Nevertheless, they o er limited performance in terms of the thermal sensitivity. Here we present, an epitaxially grown Si/Si1-xGex multi-quantum-well (MQW) detector as a potential candidate to improve the thermal sensitivity due to its inherent fringe bene t of ease of the bandgap tailoring by increasing the Ge content up to 50 %. It offers low flicker noise attributed to its single crystalline properties. The predictive technology computer-aided design (TCAD) tool has been used to obtain a priori estimate to design and develop Si/Si1-xGex MQW detector. A comprehensive predictive device model is developed to investigate the electrical characteristics of Si/Si1-xGex MQW, device design challenges and design trade-o s. The integrated self-consistent numerical modeling framework incorporates the number of interdependent design variables such as Ge content, active device areas, the doping pro les, the thickness and the periodicity of quantum wells. The model is employed to optimize Ge content and the doping pro le for the desired Figure-of merits specified in terms of the temperature coefficient of resistance (TCR) and dc resistance (R). The modeling results are validated with the experimental data and found consistent over a wide range of Ge content varied from 30% up to 50 %. The model predicts TCR can be raised up to 5.4%K-1 by incorporating 50% Ge content in MQW (experimentally verified) where the measured flicker noise constant k1=f of the detector is 5.8 10-13.
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