Study on the Temperature Dependency Effect of Thermal Coefficient of Resistance in Amorphous Silicon for Uncooled Microb
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.674
Study on the Temperature Dependency Effect of Thermal Coefficient of Resistance in Amorphous Silicon for Uncooled Microbolometer Application Junkyo Jeong1, Byeongjun Jeong1, Jaeseop Oh2, Gawon Lee1 1
Chungnam National University, Deajoen, Republic of Korea,
2
National NanoFab Center, Deajoen, Republic of Korea
ABSTRACT
In this paper, we studied the temperature dependency effect of thermal coefficient of resistance (TCR) in amorphous silicon (a-Si) on the properties of uncooled microbolometer with a-Si as a resistance layer by simulation. The temperature of the microbolometer rises during the operation mainly due to the heat generated by Joule heating as well as IR radiation. Generally, the TCR of a-Si is treated as a constant for the simplicity but the absolute value of TCR has been reported to decrease as the temperature increases. Therefore, to improve the device characteristics, the effect of temperature dependency of TCR in a-Si should be considered carefully in the range of the operating temperature. The responsivities of microbolometer are simulated according to the width of the resistance layer (W) with TCR as a function of temperature, which shows that the optimal W condition is affected by the TCR value changed by the temperature.
INTRODUCTION Every object on the earth has a constant temperature or temperature distribution. All objects emit radiant energy above 0 K, and the emission of radiant energy differs depending on the temperature of the object. Infrared (IR) detection technology refers to techniques such as detecting radiation from an object and measuring the temperature of the object or visualizing the shape of an object in an environment with no visible light. These technologies are widely applied to human body temperature measurement, motion detection, and building heat measurement [1-4].
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The method of detecting the IR radiation is divided into a thermal type and a quantum type, according to the physical quantity to be detected [5,6]. The quantum type detects the change in conductivity and photovoltaic power from the incident light, and the thermal type detects the electrical signal in accordance with the temperature change due to the absorption of the radiation energy. Generally, IR detectors are classified into the uncooled type and the cooled type, depending on the operating temperature of the detector. A thermal detector that operates at room temperature can be regarded as an uncooled type, and a quantum detector that operates at a low temperature using a cooler can be regarded as a cooled type. The cooled-type IR sensor has high sensitivity and a fast response speed, but it has to operate in a very low temperature state in order to suppress noise, which is expensive
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