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Abstract

Current inorganic semiconductor devices, including light emitting diodes (LEDs), are based mostly on groundbreaking achievements in semiconductor technology, such as fabrication of heterostructures used in high performance devices (Nobel Prize in 2000) and invention of efficient LEDs (Nobel Prize in 2014). Recently, due to the demand for electronic and optoelectronic devices with large-size and flexibility, many efforts have been made to fabricate the devices in a foldable form using inorganic, organic semiconductors, and their hybrids. For the fabrication of high performance devices, inorganic semiconductors have many advantages over organic semiconductors because of their high radiative recombination rates, high carrier mobility as well as long term stability and reliability. However, problems associated with high-quality inorganic material preparation on flexible and large-size substrates are one of the major obstacles to use inorganic semiconductors in flexible and large-scale device applications. In particular, the limited size and rigidity of typical inorganic semiconductor growth substrates require further developments of novel material system and device fabrication process suitable for the recent trend. Here, this dissertation introduces a novel material system of hybrid heterostructure, which composed of epitaxial inorganic semiconductor thin films and catalyst-free one dimensional (1D) micro- and nanostructures directly grown on graphene films, for transferable and flexible inorganic semiconductor device applications. This thesis consists of 7 parts. Following by general introduction in chapter 1, chapter 2 reviews preparation methods and characteristics of graphene briefly and discusses about graphene as an inorganic growth substrates for transferable and flexible device applications. In chapter 3, the detailed experimental set-ups and procedures, including growth, fabrication and characterization methods, are described. Chapter 4 presents a method to grow epitaxial GaN films on graphene films. GaN films were grown on various graphene films, such as mechanically exfoliated graphene layers from the graphite powder and chemical vapor deposition grown graphene films. The optical and structural characteristics of GaN films grown on various graphene substrates are also discussed. In addition to the GaN films, 1D GaN micro- and nanorods were grown on graphene films with high optical and structural quality, which are described in chapter 5. Using these hybrid heterostructures, transferable, large-scale, and flexible optoelectronic devices were fabricated in chapter 6. Finally, chapter 7 presents the summaries of this thesis with suggestion for future works.