Analysis of defect structure in GaN epilayers doped with implanted Si+ by RBS/c method

In this work, the Si⁺ doping of undoped GaN (n ∼1 × 10¹⁶ cm⁻³) on sapphire by a single step implantation or sequential implantation/recrystallization processes, to a total fluence of 1 × 10¹⁶ at/cm² and subsequent activation annealing at 1100 °C for 2 min, were demonstrated and analysed. We proved that the multicycle implantation/recrystallization process is better in terms of structural and electrical parameters of implanted region than conventional single step implantation. Rutherford backscattering spectrometry in channeling geometry (RBS/c), McChasy simulations and atomic force microscopy (AFM) studies showed, that the proposed process does not deteriorate surface morphoplogy and leads to a significantly lower defect concentrations. Low resistivity ohmic contacts, with R_C < 0.1 Ω mm, to low sheet resistivity Si-implanted GaN region (R_SH = (36.9 ± 0.7) Ω/sq.), were obtained with the use of sequential implantation with 30 s recrystallization annealing.