Electronic properties of graphene/p-silicon Schottky junction

We fabricate graphene/p-Si heterojunctions and characterize their current-voltage properties in a wide temperature range. The devices exhibit Schottky diode behaviour with a modest rectification factor up to 10(2). The Schottky parameters are estimated in the framework of the thermionic emission theory using Cheung's and Norde's methods. At room temperature, we obtain an ideality factor of about 2.5 and a Schottky barrier height of similar to 0.18 eV, which reduces at lower temperatures. We shed light on the physical mechanisms responsible for the low barrier, discussing the p-doping of graphene caused by the transfer process, the exposure to air and the out-diffusion of boron from the Si substrate. We finally propose a band model that fully explains the experimental current-voltage features, included a plateau observed in reverse current at low temperatures.