Growth at GaN/AlN hetero structures: a local view

The local structure at GaN on AlN(0001) heterostructures is studied using polarization dependent X-ray absorption spectroscopy with synchrotron radiation; the Ga K edge has been used and the analysis has been extended up to the third coordination shell. Samples have been deposited using molecular beam epitaxy with deposition temperatures in the range 620-790 degreesC and are approximately 6 mn. thick. We find that the GaN/AlN interface is abrupt (no interdiffusion) and that a partially pseudomorphically strained growth occurs, the in-plane strain increasing as the deposition temperature decreases.