Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 87: ZnO: Growth and Defects

HL 87.4: Vortrag

Freitag, 18. März 2011, 11:00–11:15, POT 51

Incorporation of dopant atoms into zinc oxide surface layers using ultrashort laser pulses — •Andreas Schneider, Apurba Dev, Kathrin Sebald, and Tobias Voß — Institut für Festkörperphysik, Bremen, Germany

The exposure of semiconductors to ultrashort laser pulses can lead to ultrafast melting and ablation of their surfaces. These non equilibrium processes create quasi-periodic surface structures. For silicon, these micro-structured surfaces - often called black silicon - show a strong increase of the absorption above and below its bandgap in a sulphurous environment creating an extremely highly doped surface layer. We apply a similar approach for zinc oxide. A thin layer of antimony is vapor-deposited on a bulk c-plane wafer followed by structuring the sample with amplified 100fs laser pulses. After multiple pulses, the zinc oxide surface shows a ripple pattern. Steep trenches run down to 3µm into the bulk. Cross sectional TEM measurements reveal a 200nm thick polycrystalline layer on top of the ripple structure. Below this layer the ripples are single crystalline. EDX measurements show that antimony was incorporated to the first 260nm, resulting in the tracing of antimony even in the single crystalline region. The exact amount of incorporation and the surface morphology strongly depend on the applied structuring parameters. Using SEM we find that increasing the laser fluence also increases the observed ripple period. In contrast to this a larger number of pulses leads to smaller ripple periods as well as steeper and deeper trenches. Our results are a promising step towards doping zinc oxide surface layers by ultrashort laser pulses.