Dresden 2011 – scientific programme

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DS: Fachverband Dünne Schichten

DS 7: Layer Properties: Electrical, Optical and Mechanical Properties

DS 7.6: Talk

Monday, March 14, 2011, 19:00–19:15, GER 37

Determination of the electrically active Al fraction in Al doped ZnO grown by pulsed reactive magnetron sputtering — •Steffen Cornelius, Mykola Vinnichenko, Frans Munnik, René Heller, Andreas Kolitsch, and Wolfhard Möller — Helmholtz Zentrum Dresden-Rossendorf, Dresden, Germany

Al-doped ZnO (AZO) films which combine maximum carrier mobility, moderate free electron densities and high surface roughness are of special interest for application as transparent front electrode in thin film solar cells. They posses high transmission in the near infrared spectral range, close to the bandgap energy of absorber materials like Si (Eg=1.11 eV), and enable a superior light trapping behaviour. A key to tailor AZO film properties is understanding the mechanisms and effects of the Al-dopant incorporation into the ZnO matrix. It is well accepted that the mobilities in degenerately doped AZO are limited by ionized impurity scattering. A way to overcome this limitation would be to reduce the density of ionized impurities which either do not donate electrons themselves or compensate the Al donor. This is equivalent to increasing the fraction of electrically active Al in the ZnO host material. Systematic and quantitative information on this topic is still missing in literature. Therefore this work focuses on quantification of the Al concentration by ion beam analysis methods in conjuction with Hall-effect measurements for AZO films grown by reactive pulsed magnetron sputtering. The influence of parameters like target composition and substrate temperature on the Al activation will be discussed.