Optical properties of aluminium nitride prepared by chemical and plasmachemical vapour deposition

Aluminium nitride films are produced on fused quartz, silicon, and spinel substrates by reaction of AlCl3 with NH3 or ammonolysis of AlCl3 · NH3 as well as by plasmachemical reaction of AlCl3 with N2 within a range of substrate temperatures of 700 to 1300 °C. The refraction index n, the absorption coefficient α, and the r. m. s.-surface roughness result from optical studies in the spectral range of 3.5 to 7.5 eV. The spectral dependence of optical constants yields a direct band gap Eg = 5.9 to 6.0 eV. Furthermore absorption bands are observed at 4.5 and 5 eV. Moreover some results for structural and electrical characterizing of films are given.