Effects of thermal annealing in ion-implanted Gallium Nitride

The effects of thermal annealing either on the electrical activation of implanted species or device isolation were investigated. Silicon implantation was used for n-type doping, Magnesium for p-type doping and/or devices edge termination, while Nitrogen for devices isolation. The ions species were implanted on n-type GaN films (2E16 cm-3) at energies between 30 and 180 keV and fluences in the range 0.1 - 5E14 cm-2. After implantation, the samples were annealed in N2 at high temperatures (about 1000 C) and different ramp rates (5 - 100 C/min). Scanning Capacitance Microscopy (SCM) was used to estimate the electrical activation and/or determine the doping concentration profile in the implanted region. For n-type Si-implantation, annealing temperatures of 1200 C were necessary to achieve a significant electrical activation of the implanted specie. An active fraction of 63% was achieved combining a conventional furnace annealing at 1200 C with a rapid annealing at 1100 C. On the other hand, in the case of Mg-implantation, SCM analyses showed a compensation of the n-type dopant after rapid annealing at 1150 C, and the formation of a p-type region upon rapid annealing at 1200 C.