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HL: Halbleiterphysik

HL 33: GaN: Preparation and characterization

HL 33.4: Vortrag

Mittwoch, 29. März 2006, 15:15–15:30, BEY 154

Nanostructering of GaN-based semiconductors with focused ion beam — •Timo Aschenbrenner, Jens Dennemarck, Stephan Figge, and Detlef Hommel — Institute of Solid State Physics, Semiconductor Epitaxy, University of Bremen, 28359 Bremen, Germany

Nowadays quantum dots and photonic crystals take an important role for light emitting devices. The manufacturing of such nanostructures on GaN-based semiconductors is difficult because on the one hand the commonly used method of wet etching is not applicable. And on the other hand the needed structure size is below the limit of photolithography.

Therefore two different approaches to achieve nanostructures were performed: Electron beam lithography and the structuring with focused ion beams (FIB). Electron beam lithography with an acceleration voltage of 30 kV and a beam current of a few pA up to 1 nA were used to define a pattern in polymethylmethacrylate (PMMA) resist on GaN-substrates. After developing the mask was transfered to GaN by chemical assisted ion beam etching (CAIBE). The resolution is limited by the size of the polymer to above 100 nm.

A FIB can be used as a direct approach for nanostructuring. In this case the resolution is only limited by the minimum diameter of the ion-beam to hole-diameter of 30 nm. But this approach has the disadventage, that ion damaged occurs. To reduce the damage different protection layers as titanium or nickel were used. The surfaces were investigated with AFM and SEM.