Microscopic parameters of materials containing GaN/AlN and InAs/AlAs hetero structures

摘要

EXAFS spectra of A_ⅢB_V heterostructures have been measured at the European Synchrotron Radiation Facility (ESRF, Grenoble, France), DUBBLE beam-line. It has been found that the first shell R_(Ga-N) interatomic distance in heterostructure GaN/AlN is equal to 1.91 A, which is 0.04 A smaller compared to crystalline GaN. For the second Ga-Ga shell an interatomic distance R_(Ga-Ga) of 3.13 A was found, which is 0.06 A smaller than in crystalline GaN. The coordination number N_(Ga-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 R_(In-As) for the heterostructure containing InAs quantum dots (QDs) is 0.04 A lower in comparison with those for the bulk InAs and is 2.58 A. The second shell interatomic distance R_(In-In) is 3.99 A, i.e. 0.29 A smaller compared to the bulk InAs. The Debye-Waller factor was found to be 0.022 A~2, the coordination number N_(In-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.