High-responsivity thermoelectric infrared detectors with stand-alone sub-micrometer polysilicon wires

A novel high-responsivity uncooled thermoelectric (TE) infrared (IR) detector is designed, fabricated and characterized. This detector features a single stand-alone polysilicon-based thermocouple (without a supporting membrane) covered by an umbrella-like optical cavity IR absorber. It is proved that the highest responsivity in the developed detectors can be achieved with only one thermocouple. Using a single thermocouple also results in a low resistance detector, which consequently limits the Johnson noise (e.g. less than 30 nv/√Hz in this work). Since the sub-micrometer polysilicon TE wires are the only heat path from the hot junction to the substrate, a superior thermal isolation is achieved. A responsivity of 1800 V W⁻¹ and a detectivity of 2* 10⁸ (cm Hz^1/2 W⁻¹) are measured from a 20  ×  20 µm detector comparable to the performance of detectors used in commercial focal planar arrays [1]. This performance in a compact and manufacturable design elevates the position of thermoelectric IR sensors as a candidate for low-power, high performance and inexpensive focal planar arrays. (paper)