High speed MSM photodetector based on Ge nanowires network

This paper presents the photoresponse characteristics of a high speed Ge nanowires (NWs) network metal-semiconductor-metal photodetector. Ge NWs with different diameters (30 nm–100 nm) were grown by a vapour-liquid-solid method on SiO 2 /Si (100) wafers. Responsivity up to 1.75 A W −1 has been observed for a 30 nm NWs device compared to 0.5 A W −1 for a 100 nm NWs detector. A large population of surface states results in higher responsivity in a smaller diameter NWs device. The high gain in photocurrent has been explained using back-to-back Schottky junctions in a NWs network. The 30 nm NWs detector shows a fast photoresponse with a rise time of 95 μ s and a fall time of 100 μ s. The observed diameter-dependent time response in network NWs devices has been explained using barrier-dominant photo-conductance.