Analysis of composition fluctuations in Al_xGa_(1-x)N

摘要

Composition fluctuations in Al_xGa_(1-x) N-layers (x=0.25 and 0.35) are investigated on an atomic scale by high-resolution transmission electron microscopy (HRTEM). The samples were grown by plasma induced molecular beam epitaxy on Al_2O_3 (0001). A strain state analysis of the cross-sectional HRTEM micrographs is performed with the digital analysis of lattice images (DALI) program package. Composition profiles on an atomic scale are derived by the measurement of the distances between intensity maxima positions in the HRTEM image. The analyses revealed different areas in the Al_xGa_(1-x)N-layers with either homogeneous or 'striped' contrast. In the striped areas the analyses indicate a strong decomposition that leads to the formation of self-organized superlattice structures.