Researchers from Bar-Ilan University in Israel and Yale University in the U.S have reported on a novel device architecture comprising graphene Schottky diode varactors. The team assessed that such devices have great potential for optoelectronics applications.
The team has shown that graphene varactor diodes exhibit significant advantages compared with existing graphene photodetectors, including elimination of high dark currents and enhancement of the external quantum efficiency (EQE).
The researchers' devices reportedly demonstrated a large photoconductive gain and EQE of up to 37%, fast photoresponse, and low leakage currents at room temperature.
The team applied thin film polycrystalline semiconductor contacts to a graphene channel, to construct lateral Schottky varactor diodes. The varactor diodes were prepared from CVD graphene on a 285 nm P+−Si/SiO2 substrate and were metallized with layers of 20/40/40 nm of Ge/Al/Pd in sequence. Varactors are voltage-tunable capacitors and therefore can be utilized for impedance matching and oscillators and modulators in the radio-frequency to terahertz range.