Investigation of growth, structural and optical properties of different phases of Ga2O3

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PhD; 2023; Centre for nano science and engineering

Among the semiconducting sesquioxides, Ga2O3 has attracted considerable research attention in recent years due to its excellent properties, including direct ultra wide band gap, optical transparency, high excitonic binding energy. These properties makes it a potential candidate for deep UV optoelectronics and power electronics applications. The Ga2O3 exhibits polymorphism which includes at least α-, β-, γ- and ϵ-/κ- phases. Among these phases most of the research has been carried out on thermodynamically stable β-polyphase, whose highly asymmetric crystal structure imparts highly non-isotropic optical and electronic properties. Aside from the fact that β-(AlxGa1–x)2O3 alloy is limited to an Aluminium mole fraction of 71 % thereby impeding the bandgap tuning, its non-polar crystal symmetry pose some challenges or would add additional steps to the device development process. These factor make it imperative to investigate other meta-stable polymorphs. There is a critical need for cost-effective and high-throughput methods for the deposition of semiconducting thin films in a wide range of industrial applications. In this research work optical and structural properties of metastable phases of Ga2O3 have been investigated which were deposited using cost-effective, easy to use and high-throughput techniques. In particular, an approach involving microwave-irradiation was employed to deposit polycrystalline thin films at sub 200 oC temperatures, and mist-CVD method was developed to achieve epitaxial thin films of high crystallinity at atmospheric pressure.