Microscopic parameters of materials containing GaN/AlN and InAs/AlAs heterostructures

EXAFS spectra of AIIIBv heterostructures have been measured at the European Synchrotron Radiation Facility (ESRF, Grenoble, France), DUBBLE beam-line. It has been found that the first shell RGa−N interatomic distance in heterostructure GaN/AlN is equal to 1.91 Å, which is 0.04 Å smaller compared to crystalline GaN. For the second Ga-Ga shell an interatomic distance RGa−Ga of 3.13 Å was found, which is 0.06 Å smaller than in crystalline GaN. The coordination number NGa−Ga was found to be 6.0. Our results suggest that this heterostructure with discrete electronic spectra contains two-dimentional islands with strong elastic strains. The first shell interatomic distance RIn−As for the heterostructure containing InAs quantum dots (QDs) is 0.04 Å lower in comparison with those for the bulk InAs and is 2.58 Å. The second shell interatomic distance RIn−In is 3.99 Å, i.e. 0.29 Å smaller compared to the bulk InAs. The Debye-Waller factor was found to be 0.022 Å2, the coordination number NIn−In∼2.0. The results obtained suggest that InAs/AlAs heterostructure with discrete electronic spectra contains three-dimentional islands with unhomogeneity of microstructure due to elastic strain relaxation.