Annealing of ion implanted gallium nitride

In this paper, we examine Si and Te ion implant damage removal in GaN as a function of implantation dose, and implantation and annealing temperature. Transmission electron microscopy shows that amorphous layers, which can result from high-dose implantation, recrystallize between 800 and 1100 degrees C to very defective polycrystalline material. Lower-dose implants (down to 5 x 10(13) cm(-2)), which are not amorphous but defective after implantation, also anneal poorly up to 1100 degrees C, leaving a coarse network of extended defects. Despite such disorder, a high fraction of Te is found to be substitutional in GaN both following implantation and after annealing. Furthermore, although elevated-temperature implants result in less disorder after implantation, this damage is also impossible to anneal out completely by 1100 degrees C. The implications of this study are that considerably higher annealing temperatures will be needed to remove damage for optimum electrical properties. (C) 1998 American Institute of Physics. [S0003-6951(98)00710-4].