Semiconductor nanostructures: synthesis, properties and device applications.

• Online Access: http://hdl.handle.net/2047/d10016338

Traditional lithographic method of making microelectronic circuit is approaching the physical limit. Semiconductor nanostructures are possible candidates for building blocks of new generation electrical and optical circuit. In this project, my goal is to fabricate semiconductor-based nanostructures and investigate their structural, electrical and optical properties. For this, a chemical vapor deposition (CVD) system, based on the vapor-liquid-solid (VLS) mechanism, for growing semiconductor nanowires, specifically GaN nanowires has been designed and assembled. Using this CVD system, single crystal GaN wurtzite nanowires has been demonstrated on Ni catalysts deposited on sapphire substrates. The wires exhibit a vertical growth with non-uniform wire diameters. In order to control the wire diameter and spacing of the nanowire growth, nanoporous alumina templates has been used a mask to control catalyst deposition and pattern the substrate. Under such conditions, we demonstrated a new epitaxially grown GaN wire growth in the zing-blende type cubic crystal structure. This is in contrast to the vertically grown wurtzite structure which is typically obtained. We have studied the detailed structural properties (using scanning and transmission electron microscopy and atomic force microscopy) for both kinds of wires has been studied. Raman spectroscopy, photoluminescence, current-voltage measurements for the nanowires are studied and possible device applications such as in transistors are investigated in this thesis.