Si implant-assisted Ohmic contacts to GaN

摘要

The contact resistance, ρ_c. was measured for the traditional Ti/Al/Ni/Au Ohmic contact for samples implanted with Si to >10~(20) cm~(-3) and annealed at 1100, 1150,1200, or 1250 ℃ for 2, 5 or 10 min using an A1N annealing cap. These results are compared with those for samples annealed in the same way, but were not implanted. The as-grown samples were doped to 3.56 × 10~(17) or 6.67 × 10~(15)cm~(-3) or were unintentionally (UI) doped. In almost all cases, pc for the implanted sample was lower, and a record low ρ_c=2.66 × 10~(-8) Ωcm~2 was achieved for the more heavily doped implanted sample annealed at 1200 ℃ for 10 min. ρ_c decreased with the doping concentration, and for the UI samples, Ohmic contacts could be made only if the samples were implanted. The surface roughness was also measured, and it was found for an as-grown with an RMS roughness of 0.303 nm, the roughness increased from 0.623 after an 1100 ℃ anneal to 3.197 nm after a 1250 ℃ anneal for the implanted samples annealed for 10 min, and it increased from 1.280 nm to 5.357 nm under the same conditions for the samples that were not implanted.