Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 87: ZnO: Growth and Defects
HL 87.2: Talk
Friday, March 18, 2011, 10:30–10:45, POT 51
Defect Reduced Growth of Pulsed Laser Deposited ZnO — •Fabian Budack, Marc A. Gluba, Lars-Peter Scheller, and N.H. Nickel — Helmholtz-Zentrum Berlin für Materialien und Energie, Kekuléstr. 5, 12489 Berlin, Germany
Zinc oxide is a transparent semiconductor with a pronounced doping asymmetry. While electron conduction is easily achieved even in nominally undoped material reliable and stable p-type doping was not yet realized. Beside hydrogen, intrinsic defects have been discussed as the origin of the prevailing n-type conduction. Understanding the conditions for the formation of native donor-like defects is a necessary step towards obtaining stable p-type ZnO.
Nominally undoped, albeit n-type, ZnO thin films have been deposited by pulsed laser ablation (PLD) on sapphire and MgO substrates under varying oxygen partial pressures. Both, structural parameters like growth rate as well as electrical properties, were investigated. It is found that the carrier concentration shows a distinct minimum at oxygen partial pressures of 5 to 7· 10−4 mbar while the mobility is nearly constant over a broad range of partial pressures. The decrease of the electron concentration is accompanied by an increasing growth rate, indicating a defect reduced growth mode in the presence of oxygen. However, a further increase of the deposition pressure leads to the formation of nanostructures, which results in new defects. This trade-off and its impact on the doping asymmetry of ZnO will be discussed.