Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 56: Optische Eigenschaften
HL 56.1: Vortrag
Freitag, 28. März 2003, 11:45–12:00, POT/81
Electronic structure of GaAs:N by soft-X-ray spectroscopy: Implications in optoelectronics — •V.N. Strocov1, P.O. Nilsson2, A. Augustsson3, T. Schmitt3, L. Gridneva3, D. Debowska-Nilsson2, R. Claessen1, A.Yu. Egorov4, V.M. Ustinov4, and Zh.I. Alferov4 — 1Universitaet Augsburg, Augsburg, Germany (email F1XVS@fy.chalmers.se) — 2Chalmers University of Technology, Goeteborg, Sweden — 3Uppsala University, Uppsala, Sweden — 4A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia
GaAs:N alloys are new materials, whose applications range from efficient solar cells to long wavelength optoelectronics. Reduction of the fundamental band gap upon incorporation of N is however associated with significant loss in optical efficiency. We have studied the N-local electronic structure of GaAs:N using soft-X-ray emission/absorption spectroscopies with their large probing depth and elemental specificity. The samples were grown by MBE using radio-frequency plasma N source. The experiments were performed in the MAX-lab at the undulator beamline I511-3 using the N 1s core level near 400 eV. The experimental emission spectra have revealed a charge transfer from the N atoms taking place the valence band maximum. In combination with strong N localization of the conduction band minimum, this reduces the overlap between the valence and conduction band wavefunctions and thus limits the optical efficiency. This problem can be circumvented by formation of N clusters. We have also discovered a k-conserving process of resonant inelastic X-ray scattering, despite the random alloy nature of GaAs:N, and explained this in terms of spectral decomposition of the N wavefunctions.