Comparison of defect structure in Si and Ge ion implanted GaN epilayers by RBS/channeling

In this work, we compared ion implantation n-type doping processes in GaN using Si+ or Ge+ ions, by conducting structural and electrical characterization. In the case of Ge+ implantation processes, we compared both the standard single implantation and the sequential doping technique. Analysis of RBS/c spectra and AFM images did not show surface degradation after each technological step (RMS < 1 nm). RBS/c studies showed that the sequential Ge+ implantation/annealing process leads to lowering of the defect concentration as compared to the single implantation process. All those doping processes resulted in low specific ohmic contact resistance RC < 1 Ω·mm. The obtained sheet resistivity of Si-implanted GaN region was RSH = 120 Ω/□, as compared to RSH of 500–530 Ω/□ for Ge-implanted GaN regions.