Mechanistic Studies of Opto-Electronic Materials and Syntheses Using Multiple Laser and Surface Diagnostics

The objective of this program was the development of novel OMCVDLCVD processes for preparation of wide band-gap semiconductors and the elucidation of the basic reaction mechanisms in these processes, so as to control the deposition rates and to improve the opto-electronic properties of the materials. The synthesis and the mechanistic elucidation of wide band-gap IIIV metal nitrides by OMCVD and LCVD, the dry-passivation of GaAs and the deposition of carbon nitride films, have been carried out with a unique UHV surface reaction system equipped with multiple gas-phase and surface species analyses. The system was constructed with joint support from the ONR and Emory University. Gas-phase species were detected by EI- and REMPI-MS, whereas surface species and structure were characterized by multiple surface diagnostic tools AES, UPS, XPS, LEED, SEM and HREELS. The systematic elucidation of the spectroscopy and the mechanisms for the thermal and photochemical decomposition reactions of individual source molecules involved in the OMCVDLCVD processes were first carried out before the actual deposition processes were conducted. We used a new nitrogen source, hydrazoic acid HN3, for the preparation of InN films with 11 elemental ratio by low-pressure CVD. The prepared films were characterized by AES, UPS, XPS, SEM, LEED and HREELS, and optical techniques such as UVvisible adsorption and photo-luminescence. InN films with very high quality SEM and UPS characteristics have been deposited on GaAs substrates without a buffer layer. Over 20 technical papers with 23 presentations were completed from these studies.