EU GaN Project Shows Diamond Promise
Researchers working on a €9 million European project claim to have demonstrated the first growth of GaN on single-crystal diamond with different surface orientations.
The team, part of the "MORGaN" "“ Materials for Robust Gallium Nitride "“ project funded under EU s Seventh Framework Programme, have fabricated epitaxial GaN on (100), (111) and (110) diamond substrates using RF-MBE.
According to their data, the films are relatively smooth, with an RMS roughness of 2.57 nm. Rocking curves produced by X-ray diffraction suggest that the GaN properties are of a higher quality when grown on (111) and (110) structures.
The three-year MORGaN project, which began in November 2008, is aiming to develop high-power electronics and sensor devices for harsh environments.
Led by Alcatel-Thales III-V Laboratories, the collaboration is focused on a new InxAl1-xN/GaN structure that was developed under "UltraGaN", a project funded through the EU's previous framework programme.
One of the project objectives already verified is the concept of an ion-sensitive FET, or "ISFET", that can be used as a pH sensor to test the acidity or alkalinity of a chemical solution.
To make the ISFET, researchers grew a boron-doped nanocrystalline diamond layer on top of an AlInN barrier. According to them, the epoxy-passivated ISFET shows reproducible sensing across the pH scale from 1 to 13.
Materials firm Element Six is heading up the MORGaN effort on diamond substrates, and delivered the first batches of both single-crystal and polycrystalline diamond wafers to the consortium.
According to project leaders, the single-crystal material was shown to be defect-free in local TEM investigations, although significant regions of non-diamond carbon have been highlighted through Raman work.
TEM has also showed dislocation networks close to the surface of the wafer, possibly the result of grinding and polishing to produce flat material.
For more details, visit the MORGaN Project web site.