IMPURITY CONTAMINATION OF GAN EPITAXIAL-FILMS FROM THE SAPPHIRE, SIC AND ZNO SUBSTRATES

Likely contamination of GaN films by impurities emanating from Al2O3, SiC, and ZnO substrates during growth has been studied by secondary io n mass spectrometry (SIMS) analysis. The defective near-substrate regi on allows impurities to incorporate more readily as compared to the mo re perfect crystal as evidenced by increased impurity levels in that r egion detected by SIMS. The SIMS measurements in GaN layers grown on S IG, ZnO, and sapphire showed large amounts of Si, Zn, and O, respectiv ely, within a region wider than the defective near-substrate layer poi nting to the possibility of impurity diffusion at growth temperatures. The qualitative trend observed is fairly clear and significant. (C) 1 997 American Institute of Physics.