Depth dependence of the tetragonal distortion of a GaN layer on Si(111) studied by Rutherford backscattering/channeling

Rutherford backscattering and channeling have been used to characterize the structure of a GaN layer grown on a Si(111) substrate. The results show that a 1.26 μm GaN epitaxial layer with a rather abrupt interface and a good crystalline quality (χmin=3.4%) can be grown on a Si(111) substrate. Using the channeling angular scan around an off-normal 〈12̄13〉 axis in the {101̄0} plane of the GaN layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, can be determined. Moreover, the depth dependence of the eT can be obtained using this technique. A fully relaxed (eT=0) GaN layer for a thickness <2.8 μm is expected.