Surface States Influence in Al Schottky Barrier of Ge Nanowires
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Surface States Influence in Al Schottky Barrier of Ge Nanowires Hanay Kamimura1.a), Ricardo A. Simon2, Olivia M. Berengue3, Cleber A. Amorim1, Adenilson J. Chiquito1 and Edson R. Leite4 1
Departamento de Física, Universidade Federal de São Carlos CEP 13565-905, CP 676, São Carlos, São Paulo, Brasil 2 Universidade Tecnológica Federal do Paraná - Campus Apucarana 3 Universidade Estadual Paulista - Unesp 4 Laboratório Interdisciplinar de Eletroquímica e Cerâmicas, Departamento de Química, Universidade Federal de São Carlos, CEP 135665-905, CP 676, São Carlos, São Paulo, Brasil a)
[email protected]
ABSTRACT Aiming the understanding of how the application to devices is affected by the presence of oxygen in semiconductor nanostructures, Al/Ge-nanowires Schottky devices were fabricated without any previous treatment to remove the native oxide from nanowires' surface, originated during the growth process. Electronic transport properties of these devices were investigated and it was observed that interface states originated from the disordered oxide layer effectively pinned the Fermi level at the Ge surface, affecting Schottky barriers. Numerical calculations were made to complement this study agreeing with experiments. INTRODUCTION Considering technological aspects, Germanium nanostructures can be very interesting since they are semiconducting with high electron mobility, in comparison to Silicon, and a small and indirect gap (0.67 eV), enabling the development of nanodevices based on pn junctions 1,2,3,4,-7 . However, the presence of surface disorder in nanowires, commonly addressed to surface native oxides which unintentionally grow on the nanowire's surface, can affect the carriers transport in nanowires, making difficult the fabrication of reliable electrical and the control of the Fermi level of the whole system. It is worth to be considered that the high surface to volume ratio in nanostructures does enhance the effect and the influence of all surfaces in transport mechanisms. In these cases the disorder usually leads to a localized behavior of carrieris transport, transitioning from a simple excitation semiconducting mechanism to a more complex one such as the variable range hopping mechanism (VRH), which arises when there exists a sufficient amount of disorder states causing the random component of the crystalline potential to be large enough to localize the electron's wave functions near the band edges8-12. In this work, temperature dependent resistance and current-voltage measurements were made in order to study the properties of fabricated electrical contacts and transport mechanisms affected by localized states on Ge nanowire due to a disordered Ge-GeO2 interface. Additionaly, we made a comparison between experimental data and numerical calculations in order to complement the study of the surface states effects on the characteristics of electrical contacts, providing the opportunity to establish a quantitative understanding of nanowire electrical properties.
NANOWIRE GROWTH The synthesis of germanium nanow
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