Gallium Nitride (GaN), a wide band gap semiconductor, has gained widespread attention owing to its unique properties like spontaneous and piezoelectric polarization, high electron mobility, high saturation velocity, combined with its high thermal stability and versatility. The significance of GaN-based lateral PN junctions cannot be overstated, given their role as fundamental components of CMOS technology. However, conventional techniques like ion implantation for p-GaN doping pose challenges due to lattice defects and disorder. Additionally, doping redistribution occurs at high annealing temperatures, reaching up to 1450°C. This thesis proposes an alternative approach utilizing in-situ selective sublimation etching and regrowth techniques in an MBE environment for novel device fabrication. Through systematic experimentation and optimization of process parameters, novel insights into the sublimation etching process are obtained. The thesis presents a comprehensive process flow for lateral PN diode realization using in-situ selective sublimation etching and regrowth, showcasing precise control over device morphology. Challenges like sample property variations and substrate coatings are addressed, underscoring the importance of uniformity in the fabrication process. Overall, this work lays the foundation for employing this novel techniques in the fabrication of high-performance semiconductor devices, including GaN-based HEMT devices with regrown contacts, thereby extending the applicability of the proposed approach.