Thermopile Infrared Detector Using Doped Polysilicon Nanocones Absorber for Selective Wavelength Absorption and Performance Enhancement

Microelectromechanical systems (MEMSs) thermopile infrared (IR) detectors have been widely applied in fields such as IR thermometry and gas detection. However, enhancing their IR absorption within the required wavelength range remains challenging. This study proposes an innovative thermopile IR detector integrated with a doped polysilicon nanocones (DPSiNCs) absorber for selective wavelength absorption and performance enhancement. The DPSiNCs were prepared through ICP maskless etching of a doped polysilicon (polySi) layer, a process compatible with traditional thermopile IR detector fabrication techniques. The nanocone structure significantly reduces the reflection of IR light, and by adjusting the doping of polySi, the wavelength range for IR absorption can be tuned. Compared to detectors without DPSiNCs, measurements indicate that detectors integrated with DPSiNCs doped with phosphorus (P) at a concentration of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times 10^{{19}}$ </tex-math></inline-formula> cm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{3}}$ </tex-math></inline-formula> exhibit a new absorption peak at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$11~\mu $ </tex-math></inline-formula>m in the IR spectrum and demonstrate superior absorptivity. Notably, by maintaining the same number and size of thermocouples, the DPSiNCs integration method has enhanced the responsivity and detectivity of the detector by 26.7% and 22.2%, respectively. In addition, the response time of detector has been decreased by 46.1% benefit of high thermal conductivity of DPSiNCs. Therefore, this study presents a novel material and technological approach for improving the performance of thermopile IR detectors.