Abstract
This paper presents a novel thermopile chip in which the resonant cavity structure was fully utilized as an absorber by an optical design. The resonant cavity absorber structure was designed using Al as anthe bottom reflective metal layer, air as the intermediate dielectric layer, and SiO2/TiN/Si3N4 sandwich layers as the top absorption layer, while the bottom reflective metal (Al) was deposited on the cold junctions of the thermopile. The simulation and calculation results show that the thermopile chip with resonant cavity absorber structure not only has great infrared absorption in the wide infrared absorption range but also can effectively prevent the cold junctions from absorbing infrared radiation and inhibit the rise of temperature. As a result, the temperature difference between the hot junctions and the cold junctions is increased, and the responsivity of the thermopile chip is further improved. Moreover, the duty cycle of the thermopile chip is greatly improved due to the double-layer suspension structure. Compared with the traditional thermopile chip structure, the sizes of the thermopile chip with the resonant cavity absorber structure can be further reduced while maintaining responsivity and specific detectivity.
Highlights
The thermopile IR detector is applied in many fields, because it has the advantages of no need for cooling and chopping, broad spectral response, low cost and simple output circuit [1,2,3,4]
The sizes of the designed thermopile chip can be further reduced while maintaining responsivity and specific detectivity compared with the three types of traditional thermopile chips
A novel thermopile chip with resonant cavity absorber structure was designed by an optical simulation in this work
Summary
The thermopile IR detector is applied in many fields, because it has the advantages of no need for cooling and chopping, broad spectral response, low cost and simple output circuit [1,2,3,4]. The porous materials with dendritic and soft structure, like tra-wide wavelength range and are typically used as the absorber of thermopile chip gold-black, can have great absorption at ultra-wide wavelength range and are typically [12,13,14,15,16,17]. These porous materials are generally too fragile and not compatible used as the absorber of thermopile chip [12,13,14,15,16,17]. Higher absorption only at 8.5–13.5 μm and lower absorption at 2.5–8 μm [20,21]
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