Light revolution: Getting the right kind of white light
Lead researcher on the project, Dr Slava Kachkanov
Figure 1. (a) and (b) show projections of the RLP onto the Qy-Qz plane for sample A and sample B measured for ω=19.424° and ω=19.357° respectively, (c) and (d) are projections of the RLP on the Qx-Qz plane for the same samples. The inclined and vertical red lines in (a) and (b) indicate lattice constants for relaxed InGaN alloys and a lattice contstant (3.189 Å) for unstrained GaN. The “tails” of RLPs correspond to the “seed” InGaN.
Gaining a better understanding of InGaN and its structure could have an impact on a number of other industries where gallium nitride (GaN) plays an important role. For instance GaN holds great potential for use in high-power microwave generators and amplifiers which can be used in microwave ovens, radar systems and even on synchrotrons.
Slava and his team used a technique called microfocus X-ray diffraction to study the thin-films of InGaN. Beamline B16 was well-suited to the job due to its high-performing compound refractive X-ray optics (CRLs), equipment capable of focusing X-rays down to a few micrometers in size, which is essential to probe selected volumes of thin InGaN layers. The finely tuned X-rays were focused onto the material and deflected by the atoms within it. The resulting diffraction pattern informed the group of the crystal structure of their material.
Figure 2. The X-ray diffraction intensity speckle pattern for sample A observed during spatial scan. Note that the image is not transformed to reciprocal space.
‘InGaN epilayer characterization by microfocused x-ray reciprocal space mapping’
V. Kachkanov, I. P. Dolbnya, K. P. O’Donnell, R. W. Martin, P. R. Edwards, and S. Pereira
Appl. Phys. Lett. 99, 181909 (2011)