We fabricate and characterize graphene/Si heterojunctions in different configurations, by extensively studying the voltage and the temperature behaviour of device parameters and optical response. In particular, we demonstrate tunable Schottky barrier height and record photo-responsivity in a new-concept device made of a single-layer CVD graphene transferred onto a matrix of nanotips patterned on n-type Si wafer. The original layout, where nano-sized graphene/Si heterojunctions alternate to graphene areas exposed to the electric field of the Si substrate, which acts both as diode cathode and transistor gate, results in a two-terminal barristor with single-bias control of the Schottky barrier. The nanotip patterning favors light absorption, and the enhancement of the electric field at the tip apex improves photo-charge separation and enables internal gain by impact ionization. These features render the device a photodetector with responsivity comparable or superior to commercial photodiodes. We prove that the multi-junction approach does not add extra-inhomogeneity to the Schottky barrier height distribution. We also introduce a modified phenomenological diode equation, which well describes the experimental I-V characteristics of a graphene/Si diode both in forward and reverse bias.

Graphene/Silicon Schottky diodes

DI BARTOLOMEO, Antonio;LUONGO, GIUSEPPE;IEMMO, LAURA;
2017

Abstract

We fabricate and characterize graphene/Si heterojunctions in different configurations, by extensively studying the voltage and the temperature behaviour of device parameters and optical response. In particular, we demonstrate tunable Schottky barrier height and record photo-responsivity in a new-concept device made of a single-layer CVD graphene transferred onto a matrix of nanotips patterned on n-type Si wafer. The original layout, where nano-sized graphene/Si heterojunctions alternate to graphene areas exposed to the electric field of the Si substrate, which acts both as diode cathode and transistor gate, results in a two-terminal barristor with single-bias control of the Schottky barrier. The nanotip patterning favors light absorption, and the enhancement of the electric field at the tip apex improves photo-charge separation and enables internal gain by impact ionization. These features render the device a photodetector with responsivity comparable or superior to commercial photodiodes. We prove that the multi-junction approach does not add extra-inhomogeneity to the Schottky barrier height distribution. We also introduce a modified phenomenological diode equation, which well describes the experimental I-V characteristics of a graphene/Si diode both in forward and reverse bias.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/4682326
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