Depth dependent tetragonal distortion of a GaN epilayer with an AlN interlayer on Si(111) studied by Rutherford backscattering/channeling

Rutherford backscattering and channeling have been used to characterize the structure of an epitaxial GaN layer grown by metal–organic chemical vapor deposition on a Si(111) substrate. Using the channeling angular scan around an off-normal axis in the {101¯0} plane of the GaN layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, was determined. Moreover, the depth dependence of the eT was obtained by this technique. Our results show that the eT of the GaN epilayer is drastically reduced from 0.41% to 0.22% by inserting a 20nm AlN interlayer. A fully relaxed (eT=0) GaN layer with a thickness of