Analysis of composition fluctuations in AlxGa1-xN

Composition fluctuations in AlxGa1-xN-layers (x = 0.25 and 0.35) are invest igated on an atomic scale by high-resolution transmission electron microsco py (HRTEM). The samples were grown by plasma induced molecular beam epitaxy on Al2O3 (0001). A strain state analysis of the cross-sectional HRTEM micr ographs is performed with the digital analysis of lattice images (DALI) pro gram package. Composition profiles on an atomic scale are derived by the me asurement of the distances between intensity maxima positions in the HRTEM image. The analyses revealed different areas in the AlxGa1-xN-layers with e ither homogeneous or 'striped' contrast. Ln the striped areas the analyses indicate a strong decomposition that leads to the formation of self-organiz ed superlattice structures. (C) 1999 Elsevier Science S.A. All rights reser ved.