Wpływ dyslokacji przechodzących na dyfuzję domieszek donorowych i akceptorowych w azotku galu

Gallium nitride (GaN)-based vertical power devices are promising candidates for future kV-class power electronics due to GaN’s wide bandgap and high critical electric field. Numerous studies have demonstrated high-performance vertical GaN power diodes and transistors with impressive breakdown voltages and low specific on-resistances nearing theoretical material limits. However, fabricating such devices poses significant challenges, particularly due to the inefficiency of selective p-type (holes) and n-type (electrons) doping technologies. One promising approach involves ion implantation of donors and acceptors into GaN, a well-established technique in silicon and silicon carbide industries but still under development for GaN. Creating well-defined n-type and p-type regions in GaN via ion implantation remains a major obstacle. Ultra-high-pressure annealing offers a solution, enabling the formation of n-type and p-type GaN with properties comparable to those of epitaxial GaN doped with appropriate donors or acceptors. A vertical GaN junction barrier Schottky diode combining ion implantation and ultra-high-pressure annealing has been successfully demonstrated. A key challenge with ion implantation in GaN is controlling the diffusion of implanted species, which can penetrate deeply into the material. The diffusion coefficient depends on factors such as structural quality including the concentration of point and linear defects, crystallographic orientation, and the Fermi level position. This project focuses on analyzing how structural quality, represented by threading dislocation density, influences the diffusion of implanted donors and acceptors in GaN. GaN-based devices can be fabricated on native or foreign substrates, each exhibiting varying structural qualities and threading dislocation densities. For example: • Native ammonothermal substrates: High structural quality with threading dislocation densities of 10³–10⁵ cm⁻². • GaN crystallized on sapphire using halide vapor phase epitaxy: Intermediate quality with densities of 10⁶–10⁷ cm⁻². • Sapphire with thin GaN layers by metal-organic vapor phase epitaxy: Lower quality with densities of 10⁸–10⁹ cm⁻². • GaN-on-silicon: Lowest quality with threading dislocation densities exceeding 10⁹ cm⁻². By growing several-micrometer-thick unintentionally doped GaN layers on these substrates, we will obtain four distinct GaN-on-X substrate structures with varying threading dislocation densities. These structures will be implanted with basic acceptors (magnesium, beryllium) and donors (silicon, germanium) and annealed under ultra-high-pressure conditions at various temperatures while maintaining constant nitrogen pressure and time. Through finite element analysis of the diffusion profiles, we aim to determine diffusion coefficients and activation energies as functions of threading dislocation density. Complementary physical characterization of the implanted GaN (using techniques such as atomic force microscopy, X-ray diffraction, secondary ion mass spectrometry, photoluminescence, Raman spectroscopy, Hall effect measurements, positron annihilation spectroscopy, and electron microscopy) will enable us in the future to design and fabricate optimized devices, such as junction barrier Schottky diodes and metal-insulator-semiconductor field-effect transistors, utilizing ion implantation.