SPECTROSCOPIC ELLIPSOMETRY STUDY ON INITIAL GROWTH-STAGES OF GAN FILMS ON GAAS(001) IN LOW-PRESSURE MOVPE

Initial growth stages of cubic GaN (c-GaN) films on GaAs(0 0 1) in low -pressure MOVPE were studied by spectroscopic ellipsometry. The GaN bu ffer layer was deposited at 500 degrees C and was then annealed at 700 degrees C with H-2/nonomethylhydrazine (MMHy) ambient. Spectroscopic ellipsometry revealed that the buffer layer thickness was increased an d the surface was roughened during the annealing process. The change o f surface morphology was also confirmed by the atomic force microscopy measurement, These observations would be associated with the nitridat ion of the GaAs substrate by the ambient MMHy and re-crystallization o f the GaN buffer layer. Spectroscopic ellipsometry is a helpful techni que to study the initial growth stages of GaN films on GaAs substrates . (C) 1998 Elsevier Science B.V. All rights reserved.