Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 50: ZnO: Tansport

HL 50.3: Vortrag

Donnerstag, 28. Februar 2008, 14:30–14:45, ER 164

ZnO-based MIS diodes — •Heiko Frenzel, Holger von Wenckstern, Holger Hochmuth, Gisela Biehne, Michael Lorenz, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig, Germany

Metal-Insulator-Semiconductor(MIS)-diodes with ZnO as the semiconductor and high-k-dielectric oxides as insulator were fabricated using pulsed laser deposition (PLD). Metal contacts were deposited either by thermal evaporation or dc sputtering. Back contacts were realized by a thin degenerated Al-doped ZnO layer [1]. The MIS-diodes were investigated by I-V, quasi-static and dynamic C-V measurements, respectively. For polycrystalline 100 nm thick Al₂O₃ films and Pt-contacts on ZnO, dielectric constants between 9 and 16 have been found. The leakage current for such samples lies in the range of picoamperes for electric fields up to 1.5 MV/cm. C-V measurements reveal a negative shift of the flatband voltage due to positive oxide charges. Annealing experiments have been carried out to improve the dielectric properties of the gate oxide and to reduce parasitic charges. The non-intentionally doped ZnO-MIS-diodes show typical n-type behavior with accumulation and depletion regime and net doping concentrations between 10¹⁴ and 10¹⁷ cm⁻³. Inversion regime should be achieved generating minority charge carriers by irradiating with ultraviolet (hf>E_g) light.

[1] H. von Wenckstern et al., Appl. Phys. Lett. 88, 092102 (2006)