Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 50: Gallium Nitride: Fabrication and Characterization

HL 50.3: Vortrag

Mittwoch, 9. März 2016, 10:00–10:15, H17

Growth of GaN nanowires on crystalline TiN films by molecular beam epitaxy — •David van Treeck, Gabriele Calabrese, Carsten Pfüller, Oliver Brandt, Lutz Geelhaar, and Sergio Fernández-Garrido — Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5--7, 10117 Berlin, Germany

The pronounced tendency of GaN to spontaneously form nanowires (NWs) on many different materials has recently been employed to fabricate GaN NW ensembles on a wide variety of substrates, ranging from amorphous dielectrics to crystalline metals. The use of metallic substrates is particularly appealing for applications because of their excellent electrical and thermal conductivity as well as their high optical reflectivity. We have recently demonstrated the growth of GaN NWs on crystalline TiN films by plasma-assisted molecular beam epitaxy [M. Wölz, et al. Nano Lett. 15, 3743 (2015)]. Here, we study the underlying growth mechanisms in detail. Our substrates consist of a Ti layer sputtered on Al2O3(0001). It is shown that the thickness of the Ti layer has a strong influence on the properties of the resulting NW ensembles. We have also investigated the formation of TiN under different conditions and the impact of the resulting TiN microstructure on the subsequent formation of GaN NWs. The combination of in situ and ex situ analytical tools allowed us to elucidate the nucleation and growth mechanisms resulting in the formation of long (>1 μm), uncoalesced, and single crystalline GaN NWs. We have found these NWs to be N-polar, and to exhibit a tilt and a comparatively small twist of 2.4° and 0.8°, respectively.