A comparative structural investigation of GaN implanted with rare earth ions at room temperature and 500 °C

The crystallographic damage induced in GaN by 300 keV rare earth ions implantation has been investigated as a function of the implantation temperature. The defect structure of GaN thin films implanted at 500 °C with Eu or Er ions with fluences ranging between 1 × 10 15 and 2 × 10 16 at./cm 2 has been compared with the case of implantation performed at room temperature (RT). Transmission electron microscopy (TEM) investigation shows that less damage is formed during implantation at the higher temperature: basal stacking faults with a majority of I 1 type and prismatic stacking faults have been observed as in GaN implanted at RT, but with a lower density. The nanocrystalline layer observed when GaN was implanted at RT with rare earth ion fluences higher than 3 × 10 15 at./cm 2, did not form for fluences up to 2 × 10 16 at./cm 2. Implantation of GaN at 500 °C through an ultrathin AlN cap points out the protective role of this cap against the GaN surface erosion that occurs from 8 × 10 15 at./cm 2. This method appears as a promising way to reduce the induced damage during the GaN implantation process.