Ion implantation of epitaxial GaN films: Damage, doping and activation

Monocrystalline GaN films grown on AlN buffer layers previously deposited on 6H-SiC(0001) wafers and having dislocation densities on the order of 10⁷ cm/cm³ beyond 0.5 μm from the initial growth interface have been achieved via chemical vapor deposition (CVD). The absence of low angle grain boundaries invariably extant in GaN films deposited on sapphire substrates and the relatively low dislocation densities and absence of stacking faults and twinning in the implantation regions of the films make them the best materials available for the study of implantation doping. In our initial study, 160 keV Si (n-type) and 120 keV Mg (p-type) with projected range ∼ 110 nm and fluences of 1e14, 5e14 and 1e15 cm^-2 were implanted at both room temperature and 550°C. The samples were characterized by Rutherford backscattering (RBS)/channeling and photoluminescence (PL) techniques before and after implantation. RBS/channeling results of virgin and as-implanted GaN for 120 keV Mg at 550°C and 1e15 cm^-2 fluence showed that even at this comparatively high dose the implantation damage is very little. However the characteristic PL signal which was present before the implantation disappeared even for the lowest dose (1e14 cm^-2). These samples were annealed in a rapid thermal annealing furnace at 1000°C, and damage recovery and dopant activation were measured by PL, RBS/channeling and Cross-Sectional TEM (XTEM).