John O. Curry edited section_Introduction_Humanity_s_demand__.tex  almost 9 years ago

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Among the many semiconducting nanowire materials, indium gallium nitride has been a material of practical interest for quite some time. As early as 1998 there had developed an extensive field of research into InGaN laser diodes\cite{Nakamura_1998}, and this research has reached fruition in the blue-violet laser diodes currently utilized in modern compact disc technology\cite{Nakamura_2000}. More recently, as InGaN has become better characterized, there has been an upsurge in interest in InGaN nanowire structures. This is due to an increase in studies in the general field of nanowires\cite{Law_2004}, which have demonstrated that nanowires possess several capacities which make them uniquely suited as structures for InGaN. A one dimensional structure minimizes the large lattice constant mismatch between InN and GaN, and the large amount of surface area present in nanowires is ideally suited to InGaN's both traditional and emerging applications for InGaN.  Indeed, The synthesis of InGaN nanowires was initially focused on the wide range of bandgaps available with InGaN, made possible by varying the stoichiometric ratio within the alloy. Any  InGaN nanowire is not an equal mixture of the three constituent elements, but rather InN and GaN alloyed, giving possible formulas of the format In$_{x}$Ga$_{1-x}$N, each having a slightly different bandgap, and thus bridging a very wide emissions spectrum. Developments in the synthesis of these nanowires have naturally focused on these band gaps, as creating conditions that allow for the full spectrum of InGaN stoichiometries is critical to any major utilization of the material's bandgap properties. This presented a major challenge to researchers of InGaN, as there is a significant difference in the lattice constants of InN and GaN\cite{O_Donnell_2001}. However, this may have in fact spurred the development and investigation of InGaN nanowires, due to the unique advantage the nanowire structure has over other arrangements and growths of InGaN. In general, nanowires have shown to be remarkably free of the strain that accompanies alloys with large differences in lattice constant\cite{Ertekin_2005}, making nanowires more attractive for those seeking to fully utilize the potential of InGaN.  Due to these properties,  nanowires have drawn attention for both traditional applications of the material, but also for altogether new purposes. Nanowire reviews show the development of InGaN structures intended for well-trod paths such as LED photoluminescence\cite{Zhuang_2011}, but also for emerging technologies such as the photochemical conversion\cite{Osterloh_2013} and storage of solar energy\cite{Yang_2010}\cite{Liu_2014}. Indeed, emerging interest in InGaN as a solar energy converter-- through both photovolataic cells and photochemical conversion-- has been the subject of tremendous research in recent years\cite{McLaughlin_2013}, due to a band gap that allows the possibility for conversion efficiencies of greater than 50 percent\cite{Sawaki}. The pace of this development has only continued in recent years, and recent work in both the light-emitting and the light absorbing qualities of InGaN nanowires is highlighted in this review.