Ultra-high sensitivity infra-red detection and temperature effects in a graphene–tellurium nanowire binary hybrid

The optoelectronic performance of hybrid devices from graphene and optically sensitive semiconductors exceeds conventional photodetectors due to a large in-built optical gain. Tellurium nanowire (TeNW), being a narrow direct band gap semiconductor (∼0.65 eV), is as an excellent potential candidate for near infra-red (NIR) detection. Here we demonstrate a new graphene–TeNW binary hybrid that exhibits a maximum photoresponsivity of ∼106 A W−1 at 175 K in the NIR regime (920 nm–1720 nm), which exceeds the photoresponsivity of the most common NIR photodetectors. The resulting noise-equivalent power (NEP) is as low as 2 × 10−18 W Hz−1/2, and the specific detectivity (D*) exceeds 5 × 1013 cm Hz1/2 W−1 (Jones). The temperature range of optimal operation, which extends up to ≈220 K and ≈260 K for 1720 nm and 920 nm excitation, respectively, is primarily limited by the electrical conductivity of the TeNW layer, and can further be improved by lowering of the defect density as well as inter-wire electronic coupling.