Rare earth ion implantation and optical activation in nitride semiconductors for multicolor emission

Abstract

In order to understand the behavior of nitride semiconductors when submitted to ion implantation, we have used 300 keV europium at fluences from 1012 to above 1017 ions cm−2. Subsequently, Rutherford backscattering (RBS), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to investigate the evolution of damage. The optical properties were investigated prior to and after annealing. It was found that the behavior of the three compounds (AlN, GaN InN) under ion implantation is rather different: whereas InN breaks down at very low fluences (∼1012 ions cm−2), the damage formation mechanisms are similar in AlN and GaN. In both compounds, extended defects such as stacking faults play a critical role. However, they exhibit different stability, as a consequence, GaN transforms to nanocrystalline state from the surface at a fluence of around 2.5 × 1015 ions cm−2, whereas AlN undergoes a chemical amorphization starting at the projected range (Rp), when implanted to extremely high Eu fluences >1017 ionscm−2. As for the optical activation, the formation of highly stable extended defects in these compounds constitutes a real challenge for the annealing of heavily doped layers, and it was noticed that for a substantial optical activation, the implantation fluences should be kept low (<1015 Eu at cm−2).