May 21, 2007
Gallium nitride nanopyramids resist radiation
The radiation hardness of gallium nitride – one of the most radiation-resistant compounds known – can be further increased by photo-electrochemical nanostructuring, claim scientists in Moldova, Russia and the US. The result could be important for making ionizing radiation detectors, microwave devices for space and military applications, and in nuclear power stations and particle accelerators.
Gallium nitride (GaN) is a promising semiconductor material for making optical and high-power, high-frequency electronic devices that are resistant to ionizing radiation, like that from protons and other high-energy particles. Until now, however, the structural response of the material to swift heavy-ion radiation had been little studied.
Ion Tiginyanu and colleagues of the Academy of Sciences in Moldova and co-workers at the Joint Institute for Nuclear Research in Russia and Virginia Commonwealth University decided to compare the damage induced by high-energy heavy ions in as-grown and electrochemically nanostructured GaN layers. The researchers showed that the radiation hardness of GaN can be increased by as much as an order of magnitude by electrochemically treating the material. They did this by using a recently developed technique, called surface-charge lithography, to etch the GaN in an aqueous solution of potassium hydroxide while it was illuminated with UV light from a 250 W mercury lamp.
The team found that the technique causes GaN to form pyramidal nanostructures (see figure). Using photoluminescence and resonant Raman scattering spectroscopy, Tiginyanu and colleagues demonstrated that the radiation hardness of the nanostructured GaN increased by more than a factor of ten in comparison with bulk GaN. "This is especially important since GaN proves to be one of the most radiation-resistant III-V compounds even in the bulk form," explained Tiginyanu. The radiation hardness was studied by exposing the samples to 85 MeV Kr+15 ions or with 130 MeV Xe+23 ions on the IC 100 cyclotron at the Flerov Laboratory of Nuclear Reactions in Dubna, near Moscow.
The results could help develop GaN-based radiation-hard microwave devices and sensors in satellite communications, nuclear power stations and accelerators, said Tiginyanu.
The researchers reported their work in Appl. Phys. Lett..
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About the author
Belle Dumé is contributing editor at nanotechweb.org