Epitaxial Growth of Metals on Semiconductors Via Electrodeposition
This chapter reviews the literature on the epitaxial growth of metals on semiconductors by electrodeposition. The known examples for Si and GaAs are described with results from in-situ characterization of their surfaces prior and during metal growth in aq
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Epitaxial Growth of Metals on Semiconductors Via Electrodeposition Karen L. Kavanagh
Abstract
This chapter reviews the literature on the epitaxial growth of metals on semiconductors by electrodeposition. The known examples for Si and GaAs are described with results from in-situ characterization of their surfaces prior and during metal growth in aqueous electrolytes. The application of electrodeposition to semiconductor nanowire contact formation is introduced.
9.1
Introduction
Epitaxy is the alignment of a growing crystal using the substrate as a template. Success is measured by the degree of perfection of the new crystal, and how well it mimics the crystallinity, and structure of the substrate. Epitaxial growth is easiest, therefore, when there is a match in lattice spacing of the two materials forming the new interface. Best results occur with clean surfaces. Semiconductor surfaces free from amorphous native oxides or other contaminants are feasible in vacuum or inert gas environments. Crystal growth techniques such as molecular beam epitaxy (MBE), metal organic vapour phase epitaxy (MOVPE), or liquid phase epitaxy (LPE), carried out in ultra-high-vacuum, flowing gas, and molten solutions, respectively, are already well known for their fabrication of single crystalline, metal-semiconductor and semiconductor-semiconductor heterostructures [1]. Such interfaces are fundamental to efficient electronic device designs, as well as to our understanding of the underlying carrier transport mechanisms. Our focus in this chapter is epitaxial growth of metals directly on semiconductors via electrodeposition. The semiconductor surface preparation and
K.L. Kavanagh (*) Department of Physics, Simon Fraser University, Burnaby, BC, Canada e-mail: [email protected] M. Stepanova and S. Dew (eds.), Nanofabrication, DOI 10.1007/978-3-7091-0424-8_9, # Springer-Verlag/Wien 2012
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metal growth occurs within an electrically conductive solution, the electrolyte, containing metal ions. Growth is determined by electronic and ionic current through the interface and deposit, driving surface reactions. We are interested primarily in aqueous electrolytes operating at temperatures feasible with liquid water. Electrodeposition is a technique that is more than 100 years old [2, 3]. It is widely used currently to deposit polycrystalline metallic layers on conducting surfaces that are not necessarily flat including automotive and aerospace components. The capability to deposit only where electrical conduction occurs is a unique advantage. The fabrication of Cu interconnections for integrated circuits has been carried out with increasing sophistication for many years via electrodeposition [4]. With the recent growing interest in nanoscale fabrication, the advantages of electrodeposited contacts to semiconductor nanowires, for example, is being investigated [5, 6]. In general, electrodeposition offers a less complex and lower cost process than the vacuum or gas flow techniques mentioned above. Chemical preparation of semico
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