High Pressure Processing of Ion Implanted GaN

Breakdown Characteristics of GaN DMISFETs Fabricated via Mg, Si and N Triple Ion Implantation

Mg-ion-implanted layers in a GaN substrate after annealing were investigated. Implanted Mg atoms precipitated along the edges of crystal defects were observed using 3D-APT. The breakdown characteristics of a GaN double-diffused vertical MISFET (DMISFET) fabricated via triple ion implantation are presented. A DMISFET with Si-ion-implanted source regions was formed in Mg-ion-implanted p-base regions, which were isolated from adjacent devices by N-ion-implanted edge termination regions. A threshold voltage of -0.5 V was obtained at a drain voltage of 0.5 V for the fabricated vertical MISFET with an estimated Mg surface concentration of 5 × 1018 cm-3. The maximum drain current and maximum transconductance in a saturation region of Vds = 100 V were 2.8 mA/mm and 0.5 mS/mm at a gate voltage of 15 V, respectively. The breakdown voltage in the off-state was 417 V. The breakdown points were determined by the boundary regions between the N- and Mg-implanted regions. By improving heat annealing methods, ion-implanted GaN DMISFETs can be a promising candidate for future high-voltage and high-power applications.

Ion Implantation into Nonconventional GaN Structures

Despite more than two decades of intensive research, ion implantation in group III nitrides is still not established as a routine technique for doping and device processing. The main challenges to overcome are the complex defect accumulation processes, as well as the high post-implant annealing temperatures necessary for efficient dopant activation. This review summarises the contents of a plenary talk, given at the Applied Nuclear Physics Conference, Prague, 2021, and focuses on recent results, obtained at Instituto Superior Técnico (Lisbon, Portugal), on ion implantation into non-conventional GaN structures, such as non-polar thin films and nanowires. Interestingly, the damage accumulation is strongly influenced by the surface orientation of the samples, as well as their dimensionality. In particular, basal stacking faults are the dominant implantation defects in c-plane GaN films, while dislocation loops predominate in a-plane samples. Ion implantation into GaN nanowires, on the other hand, causes a much smaller density of extended defects compared to thin films. Finally, recent breakthroughs concerning dopant activation are briefly reviewed, focussing on optical doping with europium and electrical doping with magnesium.

Micro- and Nanotechnology of Wide-Bandgap Semiconductors

Gallium Nitride and Related Wide-Bandgap Semiconductors (WBS) have constantly received a great amount of attention in recent years [...]