Hybrid graphene/silicon Schottky photodiode with intrinsic gating effect

We propose a hybrid device consisting of a graphene/silicon (Gr/Si) Schottky diode in parallel with a Gr/SiO 2 /Si capacitor for high-performance photodetection. The device, fabricated by transfer of commercial graphene on low-doped n-type Si substrate, achieves a photoresponse as high as 3 A W − 1 and a normalized detectivity higher than 3.5 × 10 12 cm Hz 1 / 2 W − 1 in the visible range. It exhibits a photocurrent exceeding the forward current because photo-generated minority carriers, accumulated at Si/SiO 2 interface of the Gr/SiO 2 /Si capacitor, diffuse to the Gr/Si junction. We show that the same mechanism, when due to thermally generated carriers, although usually neglected or disregarded, causes the increased leakage often measured in Gr/Si heterojunctions. We perform extensive I – V and C - V characterization at different temperatures and we measure a zero-bias Schottky barrier height of 0.52 eV at room temperature, as well as an effective Richardson constant A ** = 4 × 10 − 5 A cm − 2 K − 2 and an ideality factor n ≈ 3.6 , explained by a thin (<1 nm) oxide layer at the Gr/Si interface.