Production and characterization of RE doped amorphous AlN and SiC thin films produced by RF magnetron sputtering (WI393-20-1,2, WI393/21-1,2,3 )

Wide bandgap semiconductors doped with rare earth ions are of increasing interest for photonic applications. The reasons for this are twofold: firstly, a large bandgap (i.e. >3 eV) allows rare earth emission in the whole visible range, covering the colors blue(Tm3+), green (Tb3+), and red (Eu3+). Secondly, it is well established that conventional semiconductors like silicon quench any rare earth emission at room temperature and therefore are not suitable for technical applications. The wide bandgap semiconductor hosts like SiC, GaN and AlN are known to overcome these problem. Furthermore, bandgap engineering between these materials opens the possibility to tailor the emission properties as it has already been demonstrated in the Al1−xGaxN system. Recently, crystalline and amorphous AlN and SiC hosts have been investigated for some rare earths, showing that they may be a promising candidate to overcome the above mentioned problems. In this context we investigated the terbium doped pseudobinary compound a-(SiC)1-x(AlN)x covering almost the whole composition range x from x=0 to x = 0.94. We obtained optical bandgaps from 2.2 eV to 4.7 eV, derived from optical transmission measurements. The films were produced by radio frequency (rf) triple magnetron sputtering and showed pronounced cathodoluminescence spectra (CL) at room temperature which can be attributed to Tb3+ 4f intrashell transitions. Isochronical annealing steps for a-(SiC)0.83(AlN)0.17 from 300 ◦C to 1100 ◦C by steps of 200 ◦C and at 1150 ◦C were performed in order to activate the Tb3+ emission. At each annealing step CL spectra were recorded and the activation of peak intensity of the Tb3+ 4f intrashell transition was plotted. Considering the variation in composition we observed that at the optimal annealing temperature slightly AlN-richer films (x = 0.55) exhibit the highest CL intensities showing pronounced Tb3+ 4f intrashell transition peaks.