A thin metallic layer of zirconium nitride (ZrN) deposited on a substrate turns out to not only facilitate the formation of gallium nitride (GaN) nanowires, but also provides a low-resistance ohmic electrical contact to their bottom parts. This phenomenon enables efficient electrical control of GaN nanowire based light emitters, such as LEDs or lasers.

Semiconductor nanostructures in general, and nanowires in particular, are promising building blocks for new generation electronic devices. In contrast to planar structures commonly used nowadays, they provide material of very high crystalline quality even on substrates with a completely different crystal structure, including amorphous substrates.

However, application of nanowires in electrically-driven devices is hampered by a problem with providing electrical contact to their bottom parts. Usually, GaN nanowires are grown on silicon (Si) substrates, which facilitates their integration with existing microelectronics. On the other hand, the use of Si substrates presents challenges in optoelectronic applications due to a non-linear, resistive electrical contact of GaN to Si, which hinders the carrier transport and heat dissipation at the interface.

In our recent work published in Nanoscale vol. 17(2025), pp. 8111-8117, in collaboration with researchers from the Institute of Photonics and Electronics of the Czech Academy of Sciences in Prague, we present an analysis of electrical properties of GaN nanowires grown by molecular beam epitaxy on sapphire substrates covered with a thin metallic layer of zirconium nitride (ZrN).

Using a nanoprobe in scanning electron microscope we have shown that the zirconium nitride layer deposited on sapphire not only enhances the formation of GaN nanowires on its surface but it also provides a low-resistance ohmic electrical contact to their bottom parts. Thus the ZrN layer can play a role of backside electrical contact to the nanowires allowing efficient control of electrically-driven light emitters based on GaN nanowires, such as LEDs or lasers. Using the same experimental set-up we have presented a good rectifying characteristic of p-n junction inside a single nanowire.

Importantly, our experimental technique preserves the as-formed ZrN/nanowire interface and eliminates technological steps required for the fabrication of electrical contacts, thus preventing the unwanted modification of properties of the nanowires. Moreover, the same method enables us to detect and quantify the dispersion of properties within the nanowire ensemble, such as variations in their size, doping density, resistance, and location of the p–n junction.