Advancing Novel Device Architectures through Selective In-Situ Sublimation Etching and Regrowth of GaN in MBE
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Gallium Nitride (GaN) is a wide band gap semiconductor which continues to attract significant interest for next-generation electronic and optoelectronic devices due to its high breakdown field, excellent carrier mobility, and thermal robustness. Realizing advanced device architectures such as vertical or regrown-contact-based transistors, however, requires precise control of etching and regrowth processes at the nanoscale. Conventional ex-situ etching approaches often introduce surface contamination and damage, limiting interface quality during subsequent epitaxial growth. This thesis explores an alternative in-situ approach leveraging selective sublimation etching and regrowth of GaN within a Molecular Beam Epitaxy (MBE) system. Through systematic variation of temperature, time and substrate this study elucidates the mechanisms governing GaN sublimation & defining parameters. Optimized process conditions are then applied to demonstrate selective area etching and regrowth, achieving smooth interfaces and controlled feature definition. Using this we realize GaN pn junctions which show rectification and GaN bandedge luminescence. The proposed method establishes a contamination-free and thermodynamically stable pathway for integrating complex device geometries directly within the MBE environment. Overall, this work advances the understanding and applicability of in-situ GaN sublimation and regrowth as a versatile platform for realizing high-performance and scalable GaN-based device architectures.