Annealing-temperature-dependent defect evolution and carrier transport in Si-implanted single-crystal AlN

The dependency of thermal annealing on the annihilation of implantation-induced defects, and carrier conduction behavior in Si-implanted single-crystal AlN grown by hydride vapor phase epitaxy was investigated. Si ions were implanted into AlN at an energy of 100 keV with a dose of 1 × 1015 cm-2, followed by annealing at temperatures ranging from 1100 to 1400 °C. X-ray photoelectron spectroscopy analysis revealed that implantation-induced defective N bonding states, including defective Al–N and N–N bonds, progressively decreased with increasing annealing temperature and disappeared after annealing above 1300 °C, indicating substantial recovery of implantation-induced lattice disorder. Time-of-flight secondary ion mass spectrometry analysis showed that the profiles of Si ions implanted into AlN remained stationary up to 1200 °C, followed by a discernible onset of redistribution at 1300 °C. At 1400 °C, however, excessive dopant out-diffusion with profile broadening caused a catastrophic reduction in the retained Si dose. Contactless resistivity measurements demonstrated enhanced donor activation with increasing annealing temperature up to 1300 °C, resulting in increased carrier concentration and reduced resistivity. However, the 1400 °C-annealed sample exhibited extremely high resistance due to severe depletion of electrically active Si dopants from the near-surface region caused by excessive dopant out-diffusion. The current–voltage (I–V) characteristics of Ni/Si-implanted AlN Schottky contacts exhibited enhanced forward current and reduced turn-on voltage with increasing annealing temperature. Corresponding Log I–Log V plots revealed that trap-assisted carrier conduction was progressively suppressed with increasing annealing temperature, as evidenced by a reduction in the low-voltage slope values. Furthermore, the 1300 °C-annealed sample exhibited an additional high-voltage conduction region, indicating partial transition from trap-controlled space-charge-limited conduction to more stable bulk-limited transport after substantial defect recovery.