Elemental analysis on group-III nitrides using heavy ion ERD

Elastic recoil detection (ERD) using energetic heavy ion beams (e.g. 170 MeV I-127) is. suitable method to measure depth profiles of light and medium heavy elements in thin films. The main advantages of ERD, which makes it favorable over many other techniques for elemental analysis, is the possibility to obtain reliable and quantitative results, a sensitivity in the ppm region or a depth resolution even better than 1 nm. ERD analysis was employed to obtain quantitative information about the aluminium content x in MBE grown AlxGa1-xN layers on Al2O3 substrates. Using this stoichiometry information and the lattice constants obtained from high resolution X-ray diffraction, Vegard's law could be confirmed with high accuracy. Secondly, nitridation of heated Al2O3 substrates in NH3 atmosphere was investigated using high resolution ERD. A substantial nitrogen content on the surface of the substrate was detected which means a nearly complete ALN layer grown on the Al2O3 surface by a heat treatment only. Such a nitridation layer can be the base for further growth of nitrides on Al2O3 surfaces. As a third, the impurity content of group III nitrides was investigated in dependence on deposition conditions for both, MBE and MOCVD grown samples. In all samples investigated an oxygen concentration larger than 100 ppm was detected which is much higher than the intrinsic charge carrier density of these samples. In addition it is shown that the efficiency of p-doping by Mg may not only be hindered by hydrogen but also by carbon impurities.