Spiral room-temperature thin-filmed photo-thermoelectric THz detector based on Bi88Sb12 solid solutions

Abstract

A terahertz (THz) room-temperature photo-thermoelectric (PTE) detector based on elements of spiral shape has been proposed. The units have been fabricated on a 20 μm mica substrate from 150 nm thin films of Bi88Sb12 and copper by a thermal deposition technique. Thermoelectric Bi88Sb12 leg acted as a sensitive element due to its high absorption and spiral shape that enable heating. It also acts as a radiator to maintain a temperature difference and a thermo-electromotive force formation. A prototype of a PTE detector has been designed, fabricated, and tested at the 0.14 THz radiation frequency. Measurements showed a voltage signal of 275 μV from 1 unit, the responsivity of 50.7 mV/W. It showed a noise equivalent power of 158 nW Hz−1/2, which is 1–2 orders of magnitude higher than for bolometers and Golay cells, but is comparable with pyroelectric detectors. The response time was 2.21 s and 1.75 s according to the experiment and the simulation, respectively, which is a bit better than for pyroelectric detectors. Based on numerical simulation an improved detector design has been proposed allowing the voltage up to 800 μV from 1 unit. The proposed PTE detector possesses several significant advantages resulting from the usage of Bi88Sb12 and comprehensive design. The fabrication process is fast, low-cost, and CMOS-compatible. The design is compact and simple and requires only two materials that simultaneously act as an absorber, thermocouple, electrical contacts, and radiator. The detector operates at room temperature and can be applied in 6 G communication systems, imaging and medical diagnostics.