Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 87: ZnO: Growth and Defects
HL 87.11: Vortrag
Freitag, 18. März 2011, 13:00–13:15, POT 51
On the T2 deep level in zinc oxide thin films — •Matthias Schmidt1,2, Robert Karsthof1, Florian Schmidt1, Holger von Wenckstern1, Martin Ellguth1, Rainer Pickenhain1, Marius Grundmann1, and Gerhard Brauer2 — 1Universtity of Leipzig, Institute for Experimental Physics II, Linnéstraße 5, D-04103 Leipzig — 2Forschungszentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Postfach 51 01 19, D-01314 Dresden
For the majority of deep levels studied in n-type conducting ZnO by means of capacitance spectroscopy only the activation energy and the high temperature limit of the electron capture cross-section are known since these quantities can be evaluated easily from the temperature dependence of the trap's thermal electron emission rate.
We focused on the T2 level present in ZnO thin films grown by pulsed laser deposition. In order to tune the T2 concentration in the samples, we employed different growth and annealing conditions as well as the implantation of oxygen and zinc ions, respectively. The physical properties of T2 were studied by different deep level transient spectroscopy and photo- capacitance experiments. These experiments revealed a strong dependence of the thermal activation energy, 185meV<E<280meV, on the concentration of T2 in the sample as well as on the electric field (Poole-Frenkel effect). T2 was found to be preferentially generated under zinc rich conditions as both, the implantation of zinc ions and thermal annealing at low oxygen partial pressures increase its concentration. From photo- capacitance transients the photo- ionisation cross- section spectrum was calculated.