RESUMO
Gallium nitride (GaN) is one of the most promising materials for high-frequency devices owing to its prominent material properties. We report on the fabrication and study of a series of Schottky diodes in the ground-signal-ground topology based on individual GaN nanowires. The electrical characterization ofI-Vcurves demonstrated relatively high ideality factor value (about 6-9) in comparison to the planar Au/GaN diodes that can be attributed to the nanowire geometry. The effective barrier height in the studied structures was defined in the range of 0.25-0.4 eV. The small-signal frequency analysis was employed to study the dependency of the scattering parameters in the broad range from 0.1 to 40 GHz. The approximation fitting of the experimental data indicated the record high cutoff frequency of about 165.8 GHz.
RESUMO
The influence of hydrogen plasma treatment on the electrical and optical properties of vertical GaN nanowire (NW)/Si heterostructures synthesized via plasma assisted molecular beam epitaxy is studied. The effect of the treatment is thoroughly studied via variation of the passivation duration. Photoluminescence investigation demonstrates that the passivation affects the doping of the GaN NWs. The samples were processed as photodiodes with a top transparent electrode to obtain detailed information about the n-GaN NWs/p-Si heterointerface under illumination. The electron beam induced current measurements demonstrated the absence of potential barriers between the active parts of the diode and the contacts, indicating ohmic behavior of the latter. I-V characteristics obtained in the dark and under illumination show that hydrogen can effectively passivate the recombination centers at the GaN NWs/Si heterointerface. The optimum passivation duration, providing improved electrical properties, is found to be 10 min within the studied passivation regimes. It is demonstrated that longer treatment causes degradation of the electrical properties. The discovered phenomenon is discussed in detail.