Enhanced Signal Micro-Raman Study of SiGe Nanowires and SiGe/Si Nanowire Axial Heterojunctions Grown Using Au and Ga-Au
- PDF / 2,040,604 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 23 Downloads / 194 Views
Enhanced Signal Micro-Raman Study of SiGe Nanowires and SiGe/Si Nanowire Axial Heterojunctions Grown Using Au and Ga-Au Catalysts J.Anaya1*, A. Torres1, J.Jiménez1, C. Prieto, A.Rodríguez2, T.Rodríguez2, C. Ballesteros3 1 Optronlab Group, Dpto. Física de la Materia Condensada, Centro I+D, Universidad de Valladolid, Paseo de Belén 11, 47011 Valladolid, Spain *present address: HH Wills Physics Laboratory, University of Bristol Tyndall Avenue, Bristol BS8 1TL, UK 2 Tecnología Electrónica, E.T.S.I.T., Universidad Politécnica de Madrid, 28040 Madrid, Spain 3 Departamento de Física, Universidad Carlos III, Leganes, Spain ABSTRACT MicroRaman spectroscopy was used for the characterization of heterostructured SiGe/Si nanowires. The NWs were grown with alloyed AuGa catalysts droplets with different Ga compositions aiming to make more abrupt heterojunctions. The heterojunctions were first characterized by TEM; then the NWs were scanned by the laser beam in order to probe the heterojunction. The capability of the MicroRaman spectroscopy for studying the heterojunction is discussed. The results show that the use of catalysts with lower Ge and Si solubility (AuGa alloys) permits to achieve more abrupt junctions. INTRODUCTION Group IV semiconductor nanowires (NWs) attract a great deal of attention because of its full compatibility with complementary metal oxide semiconductor (CMOS) technology. In particular, alloyed SiGe NWs present a great interest since they permit the continuous tunability of the physical properties by the intrinsic effect of the alloy composition, and are necessary for fabricating heterostructured group IV NWs essential for the electrically driven nanodevices [1]. The SiGe alloys have excellent properties for high frequency devices; moreover, SiGe NWs present excellent properties for thermoelectric conversion and light collection for energy applications. The control of the NW composition is a step forward to the fabrication of high quality NW heterostructures (HEs). In this way, one needs to select the optimal temperature and pressure conditions for the decomposition of the Si and Ge precursors, as well as the solubility of Si and Ge atoms in the catalysts droplets. The vapour liquid solid (VLS) method presents inherent difficulties for achieving abrupt heterointerfaces, due to the reservoir effect associated with the remaining Si or Ge solved in the catalysts droplet once the corresponding precursor gas is switched off [1-3]. In this way, the use of droplets in which the solubility of the atoms, either Si or Ge, is lower shall benefit the HE abruptness. In this context, the use of alloyed AuGa catalysts droplets is expected to substantially narrow the trailing interface in SiGe/Si NW HEs, because of the reduced solubility of Ge in Ga [2,3]. The characterization of the NWs composition, and more specifically of the HEs, is a crucial issue for the optimization of the growth processes of axial HEs. MicroRaman spectroscopy is a powerful tool for studying group IV NWs. We present herein a microRaman study of SiGe/S
Data Loading...
