THERMAL ACTIVATION BEHAVIOR OF ION-IMPLANTED ALN FOR N-TYPE AND P-TYPE DOPING
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Aluminum nitride (AlN) is an intrinsically insulating semiconductor material that holds significant promise for applications in ultrawide-bandgap (UWBG) electronics and optoelectronics. However, achieving controlled electrical conductivity in AlN has proven particularly challenging. Traditional doping methods during epitaxial growth exhibit limitations, notably the "knee behavior," wherein carrier concentration does not proportionally increase with rising dopant concentrations, primarily due to electron trapping at aluminum vacancies (VAl), threading dislocations, or the formation of DX centers. To overcome these constraints, ion implantation doping has emerged as a promising alternative technique, enabling higher dopant concentrations but inevitably introducing substantial lattice damage. Precise control of thermal annealing conditions, including temperature, duration, heating and cooling rates, as well as the ambient atmosphere, is essential for repairing implantation-induced defects and ensuring effective dopant activation.In this thesis, comprehensive experiments involving ion implantation of beryllium (Be), silicon (Si), and germanium (Ge) were carried out under diverse conditions, including a systematic investigation of various AlN substrates and annealing parameters. The effects of ion implantation and annealing on surface morphology and crystal structure were evaluated using Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD). Optimization of annealing conditions effectively mitigated implantation-induced crystal damage. A significant breakthrough was potentially achieved when recent measurements using a Physical Property Measurement System (PPMS) indicated p-type conductivity in an Be doped AlN sample, which, if confirmed, would represent a pioneering achievement in the field. To conclusively confirm this finding through accurate Hall measurements, an ultra-precise shadow mask with a minimum feature size of 2 μm was designed and successfully fabricated. This also opens new avenues for further investigation into ohmic contact in UWBG semiconductor materials.