Diffusion behaviour of vanadium in GaN thin films studied by secondary ion mass spectrometry

A sandwiched multi-structure made of alternatively undoped and vanadium (V) doped GaN layers was grown on SiN-treated (0 0 0 1) sapphire substrates by atmospheric pressure metal organic chemical vapour deposition (AP-MOCVD). The V diffusion in GaN has been investigated in the temperature range of 1000-1100 deg C by using secondary ion mass spectroscopy. The diffusion coefficients were obtained through a data-fitting program based on Fick's first law. The results suggest that V diffuses faster near the GaN/sapphire interface. During annealing, V redistributed by both in- and out-diffusion mechanisms. An activation energy of 2.9 +/- 0.4 eV is estimated for V diffusion in GaN.