| Popis: |
Polycrystalline GaN thin films were successfully grown at low temperature (250 °C) by plasma-enhanced atomic layer deposition with NH3, N2, N2/H2 gas mixture and trimethylgallium (TMG) as precusor. The growth rate, crystal structure, surface composition and the valence state of the corresponding element of the GaN thin films using different nitrogen sources were characterized and examined systematically via the spectroscopic ellipsometry, the x-ray diffractometer, the x-ray photoel-ectron spectrometer. It is showed that all the GaN thin films using different nitrogen sources were polycrystalline structure and the preffered orientation were mainly (100). The films using N2 and N2/H2 gas mixture had a higher crystal quality than films using NH3. The GPC (growth rate per cycle) would increase with the increase of the N2 flow rate. The films using a suitable ratio of N2/H2 flow rate had not only a high GPC but a good crystal quality. The ratios of Ga/N element of the films using N2/H2 gas mixture were approximated to 1:1, it would increase with the ratio of the N2/H2 flow rate in the gas mixture, which is showing much effect of the ratios of N2/H2 flow rate on the nitrogen content of the thin films. |
