Interfacial abruptness study in Au Catalyzed Si1-xGex/Si/Si1-xGex Heterostructure Nanowires Grown by VLS-CVD method

Priyanka Periwal, Nicholay Sibirev, Gilles Patriarche, Virginie Brouzet, Franck Bassani, Bassem Salem, Vladimir Dubrovskii, Thierry Baron

Laboratoire  des Technologies de la Microelectronique (LTM) UMR 5129 CNRS-UJF, CEA Grenoble, 17 Rue des Martyrs , 38054 Grenoble, France

IOFFE  Physical Technical Institute of the Russian Academy of Sciences, Politekhnicheskaya 26, 194021 St. Petersburg, Russia
Laboratoire de Photonique et de Nanostructures (LPN-CNRS), Route de Nozay, 91460 Marcoussis, France
Abstract: As MOSFETs are scaled down, power dissipation remains challenge for nanoelectronics devices. To circumvent it, alternative devices such as tunnel field effect transistors are potential candidates, where the carriers are injected by quantum band to band tunneling mechanism. In this context, axial nanowire heterointerfaces with well-controlled interfacial abruptness offer an ideal structure. In this poster, we present the effect of tuning Ge concentration in a Si1-xGex part of the nanowire on the Si/Si1-xGex and Si1-xGex/Si interfacial abruptness in axial Si-SiGe heterostructure nanowires grown by the Au-catalyzed vapor-liquid-solid method. The two heterointerfaces are always asymmetric irrespective of the Ge concentration or nanowire diameter. For a fixed diameter, the value of interface abruptness decreases with increasing the Ge content for the Si/Si1-xGex interface but shows no strong Ge dependence at the Si1-xGex/Si interface where it shows a linear correlation with the nanowire diameter. To rationalize these findings, a kinetic model for the layer-by-layer growth of nanowire heterostructures from a ternary Au-Ge-Si alloy is established which predicts a discrepancy in Ge concentration in the layer and the catalyst droplet. The Ge concentration in each layer is predicted to be dependent on the composition of the preceding layer. The most abrupt heterointerface (~5 nm) is achieved by growing Si1-xGex with x=0.85 on Si in a 25 nm diameter nanowire. Finally, we consider the influence of strain induced by the lattice mismatch on the Si/Si0.15Ge0.85 nanowire heterostructure and show the absence of misfit dislocations.

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