Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 27: II-VI semiconductors

HL 27.10: Talk

Wednesday, March 28, 2007, 16:45–17:00, H13

Photocurrent spectroscopy of deep levels in ZnO thin films — •Heiko Frenzel, Holger von Wenckstern, Alexander Weber, Heidemarie Schmidt, Gisela Biehne, Holger Hochmuth, Michael Lorenz, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstr. 5, 04103, Leipzig, Germany

Fourier transform infrared photocurrent (FTIR-PC) spectroscopy has been used as complementary method to deep level transient spectroscopy (DLTS) to investigate deep defect levels in ZnO thin films grown by pulsed laser deposition (PLD) on a-sapphire substrate. FTIR-PC spectra of undoped ZnO layers show several well-resolved features between 100 meV and 500 meV due to transitions from deep defect states either to the conduction band or to the valence band. In addition to the commonly observed intrinsic levels E1 at ∼110 meV and E3 at ∼320 meV, FTIR-PC is also able to probe transitions with smaller electron capture cross-sections like L1 at ∼160 meV and L2 at ∼260 meV which are typically not observable in ZnO thin films via DLTS. Influences of growth and annealing conditions have been investigated to gather informations about the microscopic origin of deep levels in ZnO. Further results will be shown including Co- and Mn-doped ZnO thin films [1] and a N⁺-implanted ZnO single crystal [2], where acceptor like transitions are visible.

[1] M. Diaconu et al., Solid State Communications 137, 417 (2006). [2] G. Brauer et al., Phys. Rev. B 74, 045208 (2006).