Sequentially Assembled Graphene Layers on Silicon, the Role of Uncertainty Principles in Graphene-Silicon Schottky Junctions

Owing to the atomic thickness of graphene, the out-of-plane velocity of carriers is entangled with the thickness of graphene layer as well as the quasiparticle lifetime by means of the position-momentum and energy-time uncertainty principles. The out-of-plane velocity is vital for thermionic emission of carriers across the Schottky junction at graphene-silicon interface. In this report, the effect of graphene layer thickening on the electronic and optoelectronic processes is studied in hybrid graphene-silicon Schottky junctions. The thickness of graphene layer is systematically increased via sequentially assembling of chemical vapor deposited (CVD-grown) graphene layers onto silicon. The assembled graphene layers are found to behave as structurally uncoupled layers leading to a universal scaling of in-plane current with the number of assembled layers. The reverse saturation current of the graphene-silicon junctions strongly correlates with the number of assembled graphene layers indicating the critical influence of graphene layer thickness on the electronic and optoelectronic properties of graphene-silicon junctions. The experimental observations are quantitatively analyzed based on the uncertainty principles. The effect of graphene layer thickening on the concentration and diffusion length of excess photogenerated charge carriers in graphene is investigated through lateral photovoltage spectroscopy. This work sheds light on the fundamental role of uncertainty principles in the hybrid 2D/3D junctions.