Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 87: ZnO: Growth and Defects
HL 87.9: Vortrag
Freitag, 18. März 2011, 12:30–12:45, POT 51
Strain-related defects in MgxZn1−xO thin films — •Florian Schmidt, Holger von Wenckstern, and Marius Grundmann — Universität Leipzig, Institut für Experimentelle Physik II, Abteilung Halbleiterphysik, Linnéstraße 5, 04103 Leipzig
We investigated the influence of tensile and compressive strain, respectively, on the incorporation of deep levels defects in MgxZn1−xO thin films grown by pulsed-laser deposition on a-plane sapphire substrates. For ZnO it was recently shown that tensile strain induces a new defect level traceable via photoluminescence by the recombination line I12 [1]. In order to investigate thin films under tensile and compressive strain, respectively, we chose Al-doped ZnO as buffer layer, which has a larger a-lattice constant than that of ZnO and can be used as an ohmic back-contact due to its low resistivity. The a-lattice constant of MgxZn1−xO increases with x, so the Mg-content can be used to change the strain state of the thin film from tensile to compressive strain. Therefore, we changed the Mg-contents in the samples from x = 0 to 0.02. In concordance with ref. [1] we observe the I12 transition in low temperature photoluminescence measurements only if the samples are under tensile strain. Further we have found by deep level transient spectroscopy (DLTS) and Laplace DLTS that the two deep level defects, labelled T2 and E3’ in the literature, are detectable only in thin films under tensile strain. The E3’ defect level is most likely an extended defect formed to relief stress. Independent of the strain state the two defect levels E100 and E3 are detected.
[1] M. Brandt et al., Phys. Rev. B 81(7) 073306 (2010)