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Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Symmetry and structure of carbonnitrogen complexes in gallium arsenide from infrared spectroscopy and firstprinciples calculations
 Journal of applied physics 123 (2018), No.16, Art.161553 ISSN: 00218979 ISSN: 10897550 

 English 
 Journal Article 
 Fraunhofer IISB () 
Abstract
Molecularlike carbonnitrogen complexes in GaAs are investigated both experimentally and theoretically. Two characteristic highfrequency stretching modes at 1973 and 2060 cm−1, detected by Fourier transform infrared absorption (FTIR) spectroscopy, appear in carbon and nitrogenimplanted and annealed layers. From isotopic substitution, it is deduced that the chemical composition of the underlying complexes is CN2 and C2N, respectively. Piezospectroscopic FTIR measurements reveal that both centers have tetragonal symmetry. For density functional theory (DFT) calculations, linear entities are substituted for the As anion, with the axis oriented along the ⟨1 0 0⟩ direction, in accordance with the experimentally ascertained symmetry. The DFT calculations support the stability of linear NCN and CCN complexes in the GaAs host crystal in the charge states ranging from + 3 to –3. The valence bonds of the complexes are analyzed using molecularlike orbitals from DFT. It turns out that internal bonds and bonds to the lattice are essentially independent of the charge state. The calculated vibrational mode frequencies are close to the experimental values and reproduce precisely the isotopic mass splitting from FTIR experiments. Finally, the formation energies show that under thermodynamic equilibrium CN2 is more stable than C2N.